--- a/accessible/ipc/DocAccessibleChildBase.cpp
+++ b/accessible/ipc/DocAccessibleChildBase.cpp
@@ -52,17 +52,17 @@ DocAccessibleChildBase::InterfacesFor(Ac
 /* static */ void
 DocAccessibleChildBase::SerializeTree(Accessible* aRoot,
                                       nsTArray<AccessibleData>& aTree)
 {
   uint64_t id = reinterpret_cast<uint64_t>(aRoot->UniqueID());
 #if defined(XP_WIN)
   int32_t msaaId = AccessibleWrap::GetChildIDFor(aRoot);
 #endif
-  uint32_t role = aRoot->Role();
+  a11y::role role = aRoot->Role();
   uint32_t childCount = aRoot->ChildCount();
   uint32_t interfaces = InterfacesFor(aRoot);
 
   // OuterDocAccessibles are special because we don't want to serialize the
   // child doc here, we'll call PDocAccessibleConstructor in
   // NotificationController.
   MOZ_ASSERT(!aRoot->IsDoc(), "documents shouldn't be serialized");
   if (aRoot->IsOuterDoc()) {

--- a/accessible/ipc/DocAccessibleParent.cpp
+++ b/accessible/ipc/DocAccessibleParent.cpp
@@ -108,31 +108,24 @@ DocAccessibleParent::AddSubtree(ProxyAcc
                                 uint32_t aIdx, uint32_t aIdxInParent)
 {
   if (aNewTree.Length() <= aIdx) {
     NS_ERROR("bad index in serialized tree!");
     return 0;
   }
 
   const AccessibleData& newChild = aNewTree[aIdx];
-  if (newChild.Role() > roles::LAST_ROLE) {
-    NS_ERROR("invalid role");
-    return 0;
-  }
 
   if (mAccessibles.Contains(newChild.ID())) {
     NS_ERROR("ID already in use");
     return 0;
   }
 
-  auto role = static_cast<a11y::role>(newChild.Role());
-
-  ProxyAccessible* newProxy =
-    new ProxyAccessible(newChild.ID(), aParent, this, role,
-                        newChild.Interfaces());
+  ProxyAccessible* newProxy = new ProxyAccessible(
+    newChild.ID(), aParent, this, newChild.Role(), newChild.Interfaces());
 
   aParent->AddChildAt(aIdxInParent, newProxy);
   mAccessibles.PutEntry(newChild.ID())->mProxy = newProxy;
   ProxyCreated(newProxy, newChild.Interfaces());
 
 #if defined(XP_WIN)
   WrapperFor(newProxy)->SetID(newChild.MsaaID());
 #endif
@@ -391,28 +384,24 @@ DocAccessibleParent::RecvSelectionEvent(
   RefPtr<xpcAccEvent> event = new xpcAccEvent(aType, xpcTarget, xpcDoc,
                                               nullptr, false);
   nsCoreUtils::DispatchAccEvent(Move(event));
 
   return IPC_OK();
 }
 
 mozilla::ipc::IPCResult
-DocAccessibleParent::RecvRoleChangedEvent(const uint32_t& aRole)
+DocAccessibleParent::RecvRoleChangedEvent(const a11y::role& aRole)
 {
   if (mShutdown) {
     return IPC_OK();
   }
 
- if (aRole > roles::LAST_ROLE) {
-   return IPC_FAIL(this, "Child sent bad role in RoleChangedEvent");
- }
-
- mRole = static_cast<a11y::role>(aRole);
- return IPC_OK();
+  mRole = aRole;
+  return IPC_OK();
 }
 
 mozilla::ipc::IPCResult
 DocAccessibleParent::RecvBindChildDoc(PDocAccessibleParent* aChildDoc, const uint64_t& aID)
 {
   // One document should never directly be the child of another.
   // We should always have at least an outer doc accessible in between.
   MOZ_ASSERT(aID);

--- a/accessible/ipc/DocAccessibleParent.h
+++ b/accessible/ipc/DocAccessibleParent.h
@@ -101,17 +101,17 @@ public:
   virtual mozilla::ipc::IPCResult RecvFocusEvent(const uint64_t& aID,
                                                  const LayoutDeviceIntRect& aCaretRect) override;
 #endif // defined(XP_WIN)
 
   virtual mozilla::ipc::IPCResult RecvSelectionEvent(const uint64_t& aID,
                                                      const uint64_t& aWidgetID,
                                                      const uint32_t& aType) override;
 
-  mozilla::ipc::IPCResult RecvRoleChangedEvent(const uint32_t& aRole) final;
+  mozilla::ipc::IPCResult RecvRoleChangedEvent(const a11y::role& aRole) final;
 
   virtual mozilla::ipc::IPCResult RecvBindChildDoc(PDocAccessibleParent* aChildDoc, const uint64_t& aID) override;
 
   void Unbind()
   {
     if (DocAccessibleParent* parent = ParentDoc()) {
       parent->RemoveChildDoc(this);
     }

--- a/accessible/ipc/IPCTypes.h
+++ b/accessible/ipc/IPCTypes.h
@@ -2,16 +2,29 @@
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef mozilla_a11y_IPCTypes_h
 #define mozilla_a11y_IPCTypes_h
 
+#include "mozilla/a11y/Role.h"
+
+namespace IPC {
+
+template<>
+struct ParamTraits<mozilla::a11y::role>
+  : public ContiguousEnumSerializerInclusive<mozilla::a11y::role,
+                                             mozilla::a11y::role::NOTHING,
+                                             mozilla::a11y::role::LAST_ROLE>
+{
+};
+};
+
 /**
  * Since IPDL does not support preprocessing, this header file allows us to
  * define types used by PDocAccessible differently depending on platform.
  */
 
 #if defined(XP_WIN) && defined(ACCESSIBILITY)
 
 // So that we don't include a bunch of other Windows junk.

--- a/accessible/ipc/other/PDocAccessible.ipdl
+++ b/accessible/ipc/other/PDocAccessible.ipdl
@@ -5,26 +5,27 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 include protocol PFileDescriptorSet;
 include protocol PBrowser;
 
 include "mozilla/GfxMessageUtils.h";
 
 using nsIntRect from "nsRect.h";
+using mozilla::a11y::role from "mozilla/a11y/Role.h";
 using mozilla::gfx::IntSize from "mozilla/gfx/Point.h";
 using mozilla::gfx::IntPoint from "mozilla/gfx/Point.h";
 
 namespace mozilla {
 namespace a11y {
 
 struct AccessibleData
 {
   uint64_t ID;
-  uint32_t Role;
+  role Role;
   uint32_t ChildrenCount;
   uint32_t Interfaces;
 };
 
 struct ShowEventData
 {
   uint64_t ID;
   uint32_t Idx;
@@ -58,17 +59,17 @@ parent:
   async Event(uint64_t aID, uint32_t type);
   async ShowEvent(ShowEventData data, bool aFromuser);
   async HideEvent(uint64_t aRootID, bool aFromUser);
   async StateChangeEvent(uint64_t aID, uint64_t aState, bool aEnabled);
   async CaretMoveEvent(uint64_t aID, int32_t aOffset);
   async TextChangeEvent(uint64_t aID, nsString aStr, int32_t aStart, uint32_t aLen,
                         bool aIsInsert, bool aFromUser);
   async SelectionEvent(uint64_t aID, uint64_t aWidgetID, uint32_t aType);
-  async RoleChangedEvent(uint32_t aRole);
+  async RoleChangedEvent(role aRole);
 
   /*
    * Tell the parent document to bind the existing document as a new child
    * document.
    */
   async BindChildDoc(PDocAccessible aChildDoc, uint64_t aID);
 
 child:
@@ -88,17 +89,17 @@ child:
   nested(inside_sync) sync Help(uint64_t aID) returns(nsString help);
   nested(inside_sync) sync Description(uint64_t aID) returns(nsString desc);
   nested(inside_sync) sync Attributes(uint64_t aID) returns(Attribute[] attributes);
   nested(inside_sync) sync RelationByType(uint64_t aID, uint32_t aRelationType)
     returns(uint64_t[] targets);
   nested(inside_sync) sync Relations(uint64_t aID) returns(RelationTargets[] relations);
   nested(inside_sync) sync IsSearchbox(uint64_t aID) returns(bool retval);
   nested(inside_sync) sync LandmarkRole(uint64_t aID) returns(nsString landmark);
-  nested(inside_sync) sync ARIARoleAtom(uint64_t aID) returns(nsString role);
+  nested(inside_sync) sync ARIARoleAtom(uint64_t aID) returns(nsString ariaRole);
   nested(inside_sync) sync GetLevelInternal(uint64_t aID) returns(int32_t aLevel);
   async ScrollTo(uint64_t aID, uint32_t aScrollType);
   async ScrollToPoint(uint64_t aID, uint32_t aScrollType, int32_t aX,
                       int32_t aY);
 
   // AccessibleText
 
   // TextSubstring is getText in IDL.

--- a/accessible/ipc/win/DocAccessibleChild.cpp
+++ b/accessible/ipc/win/DocAccessibleChild.cpp
@@ -258,17 +258,17 @@ DocAccessibleChild::SendSelectionEvent(c
 
   PushDeferredEvent(MakeUnique<SerializedSelection>(this, aID,
                                                                 aWidgetID,
                                                                 aType));
   return true;
 }
 
 bool
-DocAccessibleChild::SendRoleChangedEvent(const uint32_t& aRole)
+DocAccessibleChild::SendRoleChangedEvent(const a11y::role& aRole)
 {
   if (IsConstructedInParentProcess()) {
     return PDocAccessibleChild::SendRoleChangedEvent(aRole);
   }
 
   PushDeferredEvent(MakeUnique<SerializedRoleChanged>(this, aRole));
   return true;
 }

--- a/accessible/ipc/win/DocAccessibleChild.h
+++ b/accessible/ipc/win/DocAccessibleChild.h
@@ -52,17 +52,17 @@ public:
   bool SendFocusEvent(const uint64_t& aID,
                       const LayoutDeviceIntRect& aCaretRect);
   bool SendTextChangeEvent(const uint64_t& aID, const nsString& aStr,
                            const int32_t& aStart, const uint32_t& aLen,
                            const bool& aIsInsert, const bool& aFromUser,
                            const bool aDoSyncCheck = true);
   bool SendSelectionEvent(const uint64_t& aID, const uint64_t& aWidgetID,
                           const uint32_t& aType);
-  bool SendRoleChangedEvent(const uint32_t& aRole);
+  bool SendRoleChangedEvent(const a11y::role& aRole);
 
   bool ConstructChildDocInParentProcess(DocAccessibleChild* aNewChildDoc,
                                         uint64_t aUniqueID, uint32_t aMsaaID);
 
   bool SendBindChildDoc(DocAccessibleChild* aChildDoc,
                         const uint64_t& aNewParentID);
 
 protected:
@@ -251,27 +251,27 @@ private:
 
     uint64_t  mID;
     uint64_t  mWidgetID;
     uint32_t  mType;
   };
 
   struct SerializedRoleChanged final : public DeferredEvent
   {
-    explicit SerializedRoleChanged(DocAccessibleChild* aTarget, uint32_t aRole)
+    explicit SerializedRoleChanged(DocAccessibleChild* aTarget, a11y::role aRole)
       : DeferredEvent(aTarget)
       , mRole(aRole)
     {}
 
     void Dispatch(DocAccessibleChild* aIPCDoc) override
     {
       Unused << aIPCDoc->SendRoleChangedEvent(mRole);
     }
 
-    uint32_t mRole;
+    a11y::role mRole;
   };
 
   struct SerializedEvent final : public DeferredEvent
   {
     SerializedEvent(DocAccessibleChild* aTarget, uint64_t aID, uint32_t aType)
       : DeferredEvent(aTarget)
       , mID(aID)
       , mType(aType)

--- a/accessible/ipc/win/PDocAccessible.ipdl
+++ b/accessible/ipc/win/PDocAccessible.ipdl
@@ -2,29 +2,30 @@
 /* vim: set ts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 include protocol PFileDescriptorSet;
 include protocol PBrowser;
 
+using mozilla::a11y::role from "mozilla/a11y/Role.h";
 using mozilla::a11y::IAccessibleHolder from "mozilla/a11y/IPCTypes.h";
 using mozilla::a11y::IDispatchHolder from "mozilla/a11y/IPCTypes.h";
 using mozilla::WindowsHandle from "ipc/IPCMessageUtils.h";
 using mozilla::LayoutDeviceIntRect from "Units.h";
 
 namespace mozilla {
 namespace a11y {
 
 struct AccessibleData
 {
   uint64_t ID;
   int32_t MsaaID;
-  uint32_t Role;
+  role Role;
   uint32_t ChildrenCount;
   uint32_t Interfaces;
 };
 
 struct ShowEventData
 {
   uint64_t ID;
   uint32_t Idx;
@@ -55,17 +56,17 @@ parent:
   async StateChangeEvent(uint64_t aID, uint64_t aState, bool aEnabled);
   async CaretMoveEvent(uint64_t aID, LayoutDeviceIntRect aCaretRect,
                        int32_t aOffset);
   async TextChangeEvent(uint64_t aID, nsString aStr, int32_t aStart, uint32_t aLen,
                         bool aIsInsert, bool aFromUser);
   sync SyncTextChangeEvent(uint64_t aID, nsString aStr, int32_t aStart,
                            uint32_t aLen, bool aIsInsert, bool aFromUser);
   async SelectionEvent(uint64_t aID, uint64_t aWidgetID, uint32_t aType);
-  async RoleChangedEvent(uint32_t aRole);
+  async RoleChangedEvent(role aRole);
   async FocusEvent(uint64_t aID, LayoutDeviceIntRect aCaretRect);
 
   /*
    * Tell the parent document to bind the existing document as a new child
    * document.
    */
   async BindChildDoc(PDocAccessible aChildDoc, uint64_t aID);
 

--- a/browser/base/content/browser-pageActions.js
+++ b/browser/base/content/browser-pageActions.js
@@ -1253,8 +1253,65 @@ BrowserPageActions.addSearchEngine = {
         let prompt = Services.prompt.getPrompt(gBrowser.contentWindow, Ci.nsIPrompt);
         prompt.QueryInterface(Ci.nsIWritablePropertyBag2);
         prompt.setPropertyAsBool("allowTabModal", true);
         prompt.alert(title, text);
       },
     });
   },
 };
+
+// share URL
+BrowserPageActions.shareURL = {
+  onShowingInPanel(buttonNode) {
+    this._cached = false;
+  },
+
+  onPlacedInPanel(buttonNode) {
+    let action = PageActions.actionForID("shareURL");
+    BrowserPageActions.takeActionTitleFromPanel(action);
+  },
+
+  onShowingSubview(panelViewNode) {
+    // We cache the providers + the UI if the user selects the share
+    // panel multiple times while the panel is open.
+    if (this._cached) {
+      return;
+    }
+
+    let sharingService = this._sharingService;
+    let url = gBrowser.selectedBrowser.currentURI;
+    let currentURI = gURLBar.makeURIReadable(url).displaySpec;
+    let shareProviders = sharingService.getSharingProviders(currentURI);
+    let fragment = document.createDocumentFragment();
+
+    shareProviders.forEach(function(share) {
+      let item = document.createElement("toolbarbutton");
+      item.setAttribute("label", share.menuItemTitle);
+      item.setAttribute("share-title", share.title);
+      item.setAttribute("image", share.image);
+      item.classList.add("subviewbutton", "subviewbutton-iconic");
+
+      item.addEventListener("command", event => {
+        let shareTitle = event.target.getAttribute("share-title");
+        if (shareTitle) {
+          sharingService.shareUrl(shareTitle, currentURI);
+        }
+        PanelMultiView.hidePopup(BrowserPageActions.panelNode);
+      });
+
+      fragment.appendChild(item);
+    });
+
+    let bodyNode = panelViewNode.querySelector(".panel-subview-body");
+    while (bodyNode.firstChild) {
+      bodyNode.firstChild.remove();
+    }
+    bodyNode.appendChild(fragment);
+    this._cached = true;
+  }
+};
+
+// Attach sharingService here so tests can override the implementation
+XPCOMUtils.defineLazyServiceGetter(BrowserPageActions.shareURL,
+                                   "_sharingService",
+                                   "@mozilla.org/widget/macsharingservice;1",
+                                   "nsIMacSharingService");

--- a/browser/base/content/browser-siteIdentity.js
+++ b/browser/base/content/browser-siteIdentity.js
@@ -50,17 +50,17 @@ var gIdentityHandler = {
    * to be able to focus it on the popupshown event.
    */
   _popupTriggeredByKeyboard: false,
 
   /**
    * RegExp used to decide if an about url should be shown as being part of
    * the browser UI.
    */
-  _secureInternalUIWhitelist: /^(?:accounts|addons|cache|config|crashes|customizing|downloads|healthreport|license|newaddon|permissions|preferences|rights|searchreset|sessionrestore|support|welcomeback)(?:[?#]|$)/i,
+  _secureInternalUIWhitelist: /^(?:accounts|addons|cache|config|crashes|customizing|downloads|healthreport|license|permissions|preferences|rights|searchreset|sessionrestore|support|welcomeback)(?:[?#]|$)/i,
 
   get _isBroken() {
     return this._state & Ci.nsIWebProgressListener.STATE_IS_BROKEN;
   },
 
   get _isSecure() {
     // If a <browser> is included within a chrome document, then this._state
     // will refer to the security state for the <browser> and not the top level

--- a/browser/base/content/browser.css
+++ b/browser/base/content/browser.css
@@ -163,41 +163,34 @@ panelview[mainview] > .panel-header {
 }
 
 .tabbrowser-tab:not([pinned]):not([fadein]) {
   max-width: 0.1px;
   min-width: 0.1px;
   visibility: hidden;
 }
 
-.tab-close-button,
-.tabbrowser-tab::after,
-.tab-background {
-  /* Explicitly set the visibility to override the value (collapsed)
-   * we inherit from #TabsToolbar[collapsed] upon opening a browser window. */
-  visibility: visible;
-}
-
+.tab-icon-image[fadein],
 .tab-close-button[fadein],
 .tabbrowser-tab[fadein]::after,
 .tab-background[fadein] {
   /* This transition is only wanted for opening tabs. */
   transition: visibility 0ms 25ms;
 }
 
+.tab-icon-image:not([fadein]),
 .tab-close-button:not([fadein]),
 .tabbrowser-tab:not([fadein])::after,
 .tab-background:not([fadein]) {
   visibility: hidden;
 }
 
 .tab-label:not([fadein]),
 .tab-throbber:not([fadein]),
-.tab-throbber-fallback:not([fadein]),
-.tab-icon-image:not([fadein]) {
+.tab-throbber-fallback:not([fadein]) {
   display: none;
 }
 
 %ifdef NIGHTLY_BUILD
 @supports -moz-bool-pref("browser.tabs.hideThrobber") {
   .tab-throbber,
   .tab-throbber-fallback {
     display: none;
@@ -1215,17 +1208,17 @@ toolbarpaletteitem[place="palette"] > #d
   overflow-x: hidden;
 }
 
 #customization-panelWrapper,
 #customization-panelWrapper > .panel-arrowcontent,
 #customization-panelHolder {
   flex-direction: column;
   display: flex;
-  min-height: calc(174px + 8em);
+  min-height: calc(174px + 9em);
 }
 
 #customization-panelWrapper {
   flex: 1 1 auto;
   height: 0; /* Don't let my contents affect ancestors' content-based sizing */
   align-items: end; /* align to the end on the cross-axis (affects arrow) */
 }
 

--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -7349,17 +7349,17 @@ var gIdentityHandler = {
    * to be able to focus it on the popupshown event.
    */
   _popupTriggeredByKeyboard: false,
 
   /**
    * RegExp used to decide if an about url should be shown as being part of
    * the browser UI.
    */
-  _secureInternalUIWhitelist: /^(?:accounts|addons|cache|config|crashes|customizing|downloads|healthreport|license|newaddon|permissions|preferences|rights|searchreset|sessionrestore|support|welcomeback)(?:[?#]|$)/i,
+  _secureInternalUIWhitelist: /^(?:accounts|addons|cache|config|crashes|customizing|downloads|healthreport|license|permissions|preferences|rights|searchreset|sessionrestore|support|welcomeback)(?:[?#]|$)/i,
 
   get _isBroken() {
     return this._state & Ci.nsIWebProgressListener.STATE_IS_BROKEN;
   },
 
   get _isSecure() {
     // If a <browser> is included within a chrome document, then this._state
     // will refer to the security state for the <browser> and not the top level

--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -435,17 +435,18 @@
            flip="slide"
            photon="true"
            position="bottomcenter topright"
            tabspecific="true"
            noautofocus="true"
            copyURL-title="&pageAction.copyLink.label;"
            emailLink-title="&emailPageCmd.label;"
            sendToDevice-title="&pageAction.sendTabToDevice.label;"
-           sendToDevice-notReadyTitle="&sendToDevice.syncNotReady.label;">
+           sendToDevice-notReadyTitle="&sendToDevice.syncNotReady.label;"
+           shareURL-title="&pageAction.shareUrl.label;">
       <panelmultiview id="pageActionPanelMultiView"
                       mainViewId="pageActionPanelMainView"
                       viewCacheId="appMenu-viewCache">
         <panelview id="pageActionPanelMainView"
                    context="pageActionContextMenu"
                    class="PanelUI-subView">
           <vbox class="panel-subview-body"/>
         </panelview>
@@ -634,18 +635,17 @@
     </toolbar>
 
     <toolbar id="TabsToolbar"
              class="titlebar-color"
              fullscreentoolbar="true"
              customizable="true"
              mode="icons"
              aria-label="&tabsToolbar.label;"
-             context="toolbar-context-menu"
-             collapsed="true">
+             context="toolbar-context-menu">
       <hbox class="titlebar-placeholder" type="pre-tabs"
             skipintoolbarset="true"/>
 
       <tabs id="tabbrowser-tabs"
             flex="1"
             setfocus="false"
             tooltip="tabbrowser-tab-tooltip"
             stopwatchid="FX_TAB_CLICK_MS">

--- a/browser/base/content/test/static/browser_parsable_script.js
+++ b/browser/base/content/test/static/browser_parsable_script.js
@@ -4,16 +4,21 @@
 /* This list allows pre-existing or 'unfixable' JS issues to remain, while we
  * detect newly occurring issues in shipping JS. It is a list of regexes
  * matching files which have errors:
  */
 const kWhitelist = new Set([
   /browser\/content\/browser\/places\/controller.js$/,
 ]);
 
+const kESModuleList = new Set([
+  /toolkit\/res\/payments\/(components|containers|mixins)\/.*.js$/,
+  /toolkit\/res\/payments\/PaymentsStore.js$/,
+]);
+
 // Normally we would use reflect.jsm to get Reflect.parse. However, if
 // we do that, then all the AST data is allocated in reflect.jsm's
 // zone. That exposes a bug in our GC. The GC collects reflect.jsm's
 // zone but not the zone in which our test code lives (since no new
 // data is being allocated in it). The cross-compartment wrappers in
 // our zone that point to the AST data never get collected, and so the
 // AST data itself is never collected. We need to GC both zones at
 // once to fix the problem.
@@ -31,26 +36,45 @@ function uriIsWhiteListed(uri) {
   for (let whitelistItem of kWhitelist) {
     if (whitelistItem.test(uri.spec)) {
       return true;
     }
   }
   return false;
 }
 
-function parsePromise(uri) {
+/**
+ * Check if a URI should be parsed as an ES module.
+ *
+ * @param uri the uri to check against the ES module list
+ * @return true if the uri should be parsed as a module, otherwise parse it as a script.
+ */
+function uriIsESModule(uri) {
+  for (let whitelistItem of kESModuleList) {
+    if (whitelistItem.test(uri.spec)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+function parsePromise(uri, parseTarget) {
   let promise = new Promise((resolve, reject) => {
     let xhr = new XMLHttpRequest();
     xhr.open("GET", uri, true);
     xhr.onreadystatechange = function() {
       if (this.readyState == this.DONE) {
         let scriptText = this.responseText;
         try {
-          info("Checking " + uri);
-          Reflect.parse(scriptText, {source: uri});
+          info(`Checking ${parseTarget} ${uri}`);
+          let parseOpts = {
+            source: uri,
+            target: parseTarget,
+          };
+          Reflect.parse(scriptText, parseOpts);
           resolve(true);
         } catch (ex) {
           let errorMsg = "Script error reading " + uri + ": " + ex;
           ok(false, errorMsg);
           resolve(false);
         }
       }
     };
@@ -113,12 +137,16 @@ add_task(async function checkAllTheJS() 
 
   // We create an array of promises so we can parallelize all our parsing
   // and file loading activity:
   await throttledMapPromises(uris, uri => {
     if (uriIsWhiteListed(uri)) {
       info("Not checking whitelisted " + uri.spec);
       return undefined;
     }
-    return parsePromise(uri.spec);
+    let target = "script";
+    if (uriIsESModule(uri)) {
+      target = "module";
+    }
+    return parsePromise(uri.spec, target);
   });
   ok(true, "All files parsed");
 });

--- a/browser/base/content/test/statuspanel/browser.ini
+++ b/browser/base/content/test/statuspanel/browser.ini
@@ -1,5 +1,7 @@
 [DEFAULT]
 support-files =
   head.js
 
 [browser_show_statuspanel_twice.js]
+[browser_show_statuspanel_idn.js]
+skip-if = webrender && verify

new file mode 100644
--- /dev/null
+++ b/browser/base/content/test/statuspanel/browser_show_statuspanel_idn.js
@@ -0,0 +1,23 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PAGE_URL = encodeURI(`data:text/html;charset=utf-8,<a id="foo" href="http://nic.xn--rhqv96g/">abc</a><span id="bar">def</span>`);
+const TEST_STATUS_TEXT = "nic.\u4E16\u754C";
+
+/**
+ * Test that if the StatusPanel displays an IDN
+ * (Bug 1450538).
+ */
+add_task(async function test_show_statuspanel_twice() {
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, TEST_PAGE_URL);
+
+  let promise = promiseStatusPanelShown(window, TEST_STATUS_TEXT);
+  ContentTask.spawn(tab.linkedBrowser, null, async () => {
+    content.document.links[0].focus();
+  });
+  await promise;
+
+  await BrowserTestUtils.removeTab(tab);
+});

--- a/browser/base/content/test/urlbar/browser.ini
+++ b/browser/base/content/test/urlbar/browser.ini
@@ -47,16 +47,18 @@ support-files =
   page_action_menu_add_search_engine_one.html
   page_action_menu_add_search_engine_many.html
   page_action_menu_add_search_engine_same_names.html
   page_action_menu_add_search_engine_0.xml
   page_action_menu_add_search_engine_1.xml
   page_action_menu_add_search_engine_2.xml
 [browser_page_action_menu_clipboard.js]
 subsuite = clipboard
+[browser_page_action_menu_share_mac.js]
+skip-if = os != "mac" # Mac only feature
 [browser_pasteAndGo.js]
 subsuite = clipboard
 [browser_removeUnsafeProtocolsFromURLBarPaste.js]
 subsuite = clipboard
 [browser_search_favicon.js]
 [browser_tabMatchesInAwesomebar.js]
 support-files =
   moz.png

new file mode 100644
--- /dev/null
+++ b/browser/base/content/test/urlbar/browser_page_action_menu_share_mac.js
@@ -0,0 +1,72 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/* global sinon */
+Services.scriptloader.loadSubScript("resource://testing-common/sinon-2.3.2.js");
+
+// Keep track of title of service we chose to share with
+let sharedTitle;
+let sharedUrl;
+
+let mockShareData = [{
+  title: "NSA",
+  menuItemTitle: "National Security Agency",
+  image: "data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEA" +
+    "LAAAAAABAAEAAAICTAEAOw=="
+}];
+
+let stub = sinon.stub(BrowserPageActions.shareURL, "_sharingService").get(() => {
+  return {
+    getSharingProviders(url) {
+      return mockShareData;
+    },
+    shareUrl(title, url) {
+      sharedUrl = url;
+      sharedTitle = title;
+    }
+  };
+});
+
+registerCleanupFunction(async function() {
+  stub.restore();
+  delete window.sinon;
+  await EventUtils.synthesizeNativeMouseMove(document.documentElement, 0, 0);
+  await PlacesUtils.history.clear();
+});
+
+add_task(async function shareURL() {
+  // Open an actionable page so that the main page action button appears.  (It
+  // does not appear on about:blank for example.)
+  let url = "http://example.org/";
+
+  await BrowserTestUtils.withNewTab(url, async () => {
+    // Open the panel.
+    await promisePageActionPanelOpen();
+
+    // Click Share URL.
+    let shareURLButton = document.getElementById("pageAction-panel-shareURL");
+    let viewPromise = promisePageActionViewShown();
+    EventUtils.synthesizeMouseAtCenter(shareURLButton, {});
+
+    let view = await viewPromise;
+    let body = document.getElementById(view.id + "-body");
+
+    Assert.equal(body.childNodes.length, 1, "Has correct share receivers");
+    let shareButton = body.childNodes[0];
+    Assert.equal(shareButton.label, mockShareData[0].menuItemTitle);
+    let hiddenPromise = promisePageActionPanelHidden();
+    // Click on share, panel should hide and sharingService should be
+    // given the title of service to share with
+    EventUtils.synthesizeMouseAtCenter(shareButton, {});
+    await hiddenPromise;
+
+    Assert.equal(sharedTitle, mockShareData[0].title,
+                 "Shared with the correct title");
+    Assert.equal(sharedUrl, "http://example.org/",
+                 "Shared correct URL");
+
+  });
+});

--- a/browser/base/content/test/urlbar/browser_search_favicon.js
+++ b/browser/base/content/test/urlbar/browser_search_favicon.js
@@ -6,16 +6,20 @@ registerCleanupFunction(() => {
   Services.prefs.clearUserPref(gRestyleSearchesPref);
   Services.search.currentEngine = gOriginalEngine;
   Services.search.removeEngine(gEngine);
   return PlacesUtils.history.clear();
 });
 
 add_task(async function() {
   Services.prefs.setBoolPref(gRestyleSearchesPref, true);
+
+  // This test is sensitive to the mouse position hovering awesome
+  // bar elements, so make sure it doesnt
+  await EventUtils.synthesizeNativeMouseMove(document.documentElement, 0, 0);
 });
 
 add_task(async function() {
 
   Services.search.addEngineWithDetails("SearchEngine", "", "", "",
                                        "GET", "http://s.example.com/search");
   gEngine = Services.search.getEngineByName("SearchEngine");
   gEngine.addParam("q", "{searchTerms}", null);

--- a/browser/base/content/urlbarBindings.xml
+++ b/browser/base/content/urlbarBindings.xml
@@ -2452,23 +2452,27 @@ file, You can obtain one at http://mozil
       <handler event="mousedown"><![CDATA[
         // Required to make the xul:label.text-link elements in the search
         // suggestions notification work correctly when clicked on Linux.
         // This is copied from the mousedown handler in
         // browser-search-autocomplete-result-popup, which apparently had a
         // similar problem.
         event.preventDefault();
 
+        if (event.button == 2) {
+          // Right mouse button currently allows to select.
+          this.input.userSelectionBehavior = "rightClick";
+          // Ignore right-clicks.
+          return;
+        }
+
         if (!this.input.speculativeConnectEnabled) {
           return;
         }
-        if (event.button == 2) {
-          // Ignore right-clicks.
-          return;
-        }
+
         // Ensure the user is clicking on an url instead of other buttons
         // on the popup.
         let elt = event.originalTarget;
         while (elt && elt.localName != "richlistitem" && elt != this) {
           elt = elt.parentNode;
         }
         if (!elt || elt.localName != "richlistitem") {
           return;

--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -711,17 +711,17 @@ BrowserGlue.prototype = {
     LightweightThemeManager.addBuiltInTheme({
       id: "firefox-compact-dark@mozilla.org",
       name: gBrowserBundle.GetStringFromName("darkTheme.name"),
       description: gBrowserBundle.GetStringFromName("darkTheme.description"),
       iconURL: "resource:///chrome/browser/content/browser/defaultthemes/dark.icon.svg",
       textcolor: "white",
       accentcolor: "black",
       popup: "#4a4a4f",
-      popup_text: "rgba(249, 249, 250, 0.8)",
+      popup_text: "rgb(249, 249, 250)",
       popup_border: "#27272b",
       author: vendorShortName,
     });
 
     Normandy.init();
 
     // Initialize the default l10n resource sources for L10nRegistry.
     let locales = Services.locale.getPackagedLocales();

--- a/browser/locales/en-US/chrome/browser/browser.dtd
+++ b/browser/locales/en-US/chrome/browser/browser.dtd
@@ -989,16 +989,18 @@ you can use these alternative items. Oth
 <!ENTITY pageAction.removeFromUrlbar.label "Remove from Address Bar">
 <!ENTITY pageAction.allowInUrlbar.label "Show in Address Bar">
 <!ENTITY pageAction.disallowInUrlbar.label "Don’t Show in Address Bar">
 <!ENTITY pageAction.manageExtension.label "Manage Extension…">
 
 <!ENTITY pageAction.sendTabToDevice.label "Send Tab to Device">
 <!ENTITY sendToDevice.syncNotReady.label "Syncing Devices…">
 
+<!ENTITY pageAction.shareUrl.label "Share">
+
 <!ENTITY libraryButton.tooltip "View history, saved bookmarks, and more">
 
 <!-- LOCALIZATION NOTE: (accessibilityIndicator.tooltip): This is used to
      display a tooltip for accessibility indicator in toolbar/tabbar. It is also
      used as a textual label for the indicator used by assistive technology
      users. -->
 <!ENTITY accessibilityIndicator.tooltip "Accessibility Features Enabled">
 

--- a/browser/modules/BrowserUsageTelemetry.jsm
+++ b/browser/modules/BrowserUsageTelemetry.jsm
@@ -78,16 +78,17 @@ const URLBAR_SELECTED_RESULT_TYPES = {
  * these category names directly when they add to a histogram.
  */
 const URLBAR_SELECTED_RESULT_METHODS = {
   enter: 0,
   enterSelection: 1,
   click: 2,
   arrowEnterSelection: 3,
   tabEnterSelection: 4,
+  rightClickEnter: 5,
 };
 
 
 const MINIMUM_TAB_COUNT_INTERVAL_MS = 5 * 60 * 1000; // 5 minutes, in ms
 
 
 function getOpenTabsAndWinsCounts() {
   let tabCount = 0;
@@ -560,16 +561,20 @@ let BrowserUsageTelemetry = {
     } else if (highlightedIndex >= 0) {
       switch (userSelectionBehavior) {
       case "tab":
         category = "tabEnterSelection";
         break;
       case "arrow":
         category = "arrowEnterSelection";
         break;
+      case "rightClick":
+        // Selected by right mouse button.
+        category = "rightClickEnter";
+        break;
       default:
         category = "enterSelection";
       }
     } else {
       category = "enter";
     }
     histogram.add(category);
   },

--- a/browser/modules/ExtensionsUI.jsm
+++ b/browser/modules/ExtensionsUI.jsm
@@ -92,23 +92,16 @@ var ExtensionsUI = {
         };
         AddonManager.addAddonListener(this.sideloadListener);
       }
 
       for (let addon of sideloaded) {
         this.sideloaded.add(addon);
       }
         this._updateNotifications();
-    } else {
-      // This and all the accompanying about:newaddon code can eventually
-      // be removed.  See bug 1331521.
-      let win = RecentWindow.getMostRecentBrowserWindow();
-      for (let addon of sideloaded) {
-        win.openTrustedLinkIn(`about:newaddon?id=${addon.id}`, "tab");
-      }
     }
   },
 
   async _checkNewDistroAddons() {
     let newDistroAddons = AddonManagerPrivate.getNewDistroAddons();
     if (!newDistroAddons) {
       return;
     }

--- a/browser/modules/PageActions.jsm
+++ b/browser/modules/PageActions.jsm
@@ -1162,16 +1162,35 @@ if (Services.prefs.getBoolPref("identity
     },
     onSubviewShowing(panelViewNode) {
       browserPageActions(panelViewNode).sendToDevice
         .onShowingSubview(panelViewNode);
     },
   });
 }
 
+if (AppConstants.platform == "macosx") {
+  gBuiltInActions.push(
+  // Share URL
+  {
+    id: "shareURL",
+    title: "shareURL-title",
+    onShowingInPanel(buttonNode) {
+      browserPageActions(buttonNode).shareURL.onShowingInPanel(buttonNode);
+    },
+    onPlacedInPanel(buttonNode) {
+      browserPageActions(buttonNode).shareURL.onPlacedInPanel(buttonNode);
+    },
+    wantsSubview: true,
+    onSubviewShowing(panelViewNode) {
+        browserPageActions(panelViewNode).shareURL
+          .onShowingSubview(panelViewNode);
+    },
+  });
+}
 
 /**
  * Gets a BrowserPageActions object in a browser window.
  *
  * @param  obj
  *         Either a DOM node or a browser window.
  * @return The BrowserPageActions object in the browser window related to the
  *         given object.

--- a/browser/modules/test/browser/browser_UsageTelemetry_urlbar.js
+++ b/browser/modules/test/browser/browser_UsageTelemetry_urlbar.js
@@ -47,33 +47,63 @@ let searchInAwesomebar = async function(
                                                 Ci.nsIAutoCompleteController.STATUS_COMPLETE_NO_MATCH);
 };
 
 /**
  * Click one of the entries in the urlbar suggestion popup.
  *
  * @param {String} entryName
  *        The name of the elemet to click on.
+ * @param {Number} button [optional]
+ *        which button to click.
  */
-function clickURLBarSuggestion(entryName) {
+function clickURLBarSuggestion(entryName, button = 1) {
   // The entry in the suggestion list should follow the format:
   // "<search term> <engine name> Search"
   const expectedSuggestionName = entryName + " " + SUGGESTION_ENGINE_NAME + " Search";
   return BrowserTestUtils.waitForCondition(() => {
     for (let child of gURLBar.popup.richlistbox.children) {
       if (child.label === expectedSuggestionName) {
         // This entry is the search suggestion we're looking for.
-        child.click();
+        if (button == 1)
+          child.click();
+        else if (button == 2) {
+          EventUtils.synthesizeMouseAtCenter(child, {type: "mousedown", button: 2});
+        }
         return true;
       }
     }
     return false;
   }, "Waiting for the expected suggestion to appear");
 }
 
+/**
+ * Create an engine to generate search suggestions and add it as default
+ * for this test.
+ */
+async function withNewSearchEngine(taskFn) {
+  const url = getRootDirectory(gTestPath) + "usageTelemetrySearchSuggestions.xml";
+  let suggestionEngine = await new Promise((resolve, reject) => {
+    Services.search.addEngine(url, null, "", false, {
+      onSuccess(engine) { resolve(engine); },
+      onError() { reject(); }
+    });
+  });
+
+  let previousEngine = Services.search.currentEngine;
+  Services.search.currentEngine = suggestionEngine;
+
+  try {
+    await taskFn(suggestionEngine);
+  } finally {
+    Services.search.currentEngine = previousEngine;
+    Services.search.removeEngine(suggestionEngine);
+  }
+}
+
 add_task(async function setup() {
   // Create a new search engine.
   Services.search.addEngineWithDetails("MozSearch", "", "mozalias", "", "GET",
                                        "http://example.com/?q={searchTerms}");
 
   // Make it the default search engine.
   let engine = Services.search.getEngineByName("MozSearch");
   let originalEngine = Services.search.currentEngine;
@@ -115,17 +145,16 @@ add_task(async function setup() {
     Services.prefs.setBoolPref(SUGGEST_URLBAR_PREF, suggestionsEnabled);
     Services.prefs.clearUserPref(ONEOFF_URLBAR_PREF);
     await PlacesUtils.history.clear();
     Services.telemetry.setEventRecordingEnabled("navigation", false);
   });
 });
 
 add_task(async function test_simpleQuery() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
   Services.telemetry.clearEvents();
 
   let resultIndexHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_INDEX");
   let resultTypeHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_TYPE");
   let resultIndexByTypeHist = getAndClearKeyedHistogram("FX_URLBAR_SELECTED_RESULT_INDEX_BY_TYPE");
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
   let search_hist = getAndClearKeyedHistogram("SEARCH_COUNTS");
@@ -170,17 +199,16 @@ add_task(async function test_simpleQuery
   checkHistogramResults(resultMethods,
     URLBAR_SELECTED_RESULT_METHODS.enter,
     "FX_URLBAR_SELECTED_RESULT_METHOD");
 
   BrowserTestUtils.removeTab(tab);
 });
 
 add_task(async function test_searchAlias() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
   Services.telemetry.clearEvents();
 
   let resultIndexHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_INDEX");
   let resultTypeHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_TYPE");
   let resultIndexByTypeHist = getAndClearKeyedHistogram("FX_URLBAR_SELECTED_RESULT_INDEX_BY_TYPE");
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
   let search_hist = getAndClearKeyedHistogram("SEARCH_COUNTS");
@@ -227,17 +255,16 @@ add_task(async function test_searchAlias
     "FX_URLBAR_SELECTED_RESULT_METHOD");
 
   BrowserTestUtils.removeTab(tab);
 });
 
 // Performs a search using the first result, a one-off button, and the Return
 // (Enter) key.
 add_task(async function test_oneOff_enter() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
   Services.telemetry.clearEvents();
 
   let resultIndexHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_INDEX");
   let resultTypeHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_TYPE");
   let resultIndexByTypeHist = getAndClearKeyedHistogram("FX_URLBAR_SELECTED_RESULT_INDEX_BY_TYPE");
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
   let search_hist = getAndClearKeyedHistogram("SEARCH_COUNTS");
@@ -288,61 +315,45 @@ add_task(async function test_oneOff_ente
 
   BrowserTestUtils.removeTab(tab);
 });
 
 // Performs a search using the second result, a one-off button, and the Return
 // (Enter) key.  This only tests the FX_URLBAR_SELECTED_RESULT_METHOD histogram
 // since test_oneOff_enter covers everything else.
 add_task(async function test_oneOff_enterSelection() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
-
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
 
-  // Create an engine to generate search suggestions and add it as default
-  // for this test.
-  const url = getRootDirectory(gTestPath) + "usageTelemetrySearchSuggestions.xml";
-  let suggestionEngine = await new Promise((resolve, reject) => {
-    Services.search.addEngine(url, null, "", false, {
-      onSuccess(engine) { resolve(engine); },
-      onError() { reject(); }
-    });
-  });
+  await withNewSearchEngine(async function() {
+    let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
 
-  let previousEngine = Services.search.currentEngine;
-  Services.search.currentEngine = suggestionEngine;
-
-  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
+    info("Type a query. Suggestions should be generated by the test engine.");
+    let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+    await searchInAwesomebar("query");
 
-  info("Type a query. Suggestions should be generated by the test engine.");
-  let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
-  await searchInAwesomebar("query");
+    info("Select the second result, press Alt+Down to take us to the first one-off engine.");
+    EventUtils.synthesizeKey("KEY_ArrowDown");
+    EventUtils.synthesizeKey("KEY_ArrowDown", {altKey: true});
+    EventUtils.synthesizeKey("KEY_Enter");
+    await p;
 
-  info("Select the second result, press Alt+Down to take us to the first one-off engine.");
-  EventUtils.synthesizeKey("KEY_ArrowDown");
-  EventUtils.synthesizeKey("KEY_ArrowDown", {altKey: true});
-  EventUtils.synthesizeKey("KEY_Enter");
-  await p;
+    let resultMethods = resultMethodHist.snapshot();
+    checkHistogramResults(resultMethods,
+      URLBAR_SELECTED_RESULT_METHODS.arrowEnterSelection,
+      "FX_URLBAR_SELECTED_RESULT_METHOD");
 
-  let resultMethods = resultMethodHist.snapshot();
-  checkHistogramResults(resultMethods,
-    URLBAR_SELECTED_RESULT_METHODS.arrowEnterSelection,
-    "FX_URLBAR_SELECTED_RESULT_METHOD");
-
-  Services.search.currentEngine = previousEngine;
-  Services.search.removeEngine(suggestionEngine);
-  BrowserTestUtils.removeTab(tab);
+    BrowserTestUtils.removeTab(tab);
+  });
 });
 
 // Performs a search using a click on a one-off button.  This only tests the
 // FX_URLBAR_SELECTED_RESULT_METHOD histogram since test_oneOff_enter covers
 // everything else.
 add_task(async function test_oneOff_click() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
 
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
 
   let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
 
   info("Type a query.");
   let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
@@ -356,202 +367,168 @@ add_task(async function test_oneOff_clic
     URLBAR_SELECTED_RESULT_METHODS.click,
     "FX_URLBAR_SELECTED_RESULT_METHOD");
 
   BrowserTestUtils.removeTab(tab);
 });
 
 // Clicks the first suggestion offered by the test search engine.
 add_task(async function test_suggestion_click() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
   Services.telemetry.clearEvents();
 
   let resultIndexHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_INDEX");
   let resultTypeHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_TYPE");
   let resultIndexByTypeHist = getAndClearKeyedHistogram("FX_URLBAR_SELECTED_RESULT_INDEX_BY_TYPE");
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
   let search_hist = getAndClearKeyedHistogram("SEARCH_COUNTS");
 
-  // Create an engine to generate search suggestions and add it as default
-  // for this test.
-  const url = getRootDirectory(gTestPath) + "usageTelemetrySearchSuggestions.xml";
-  let suggestionEngine = await new Promise((resolve, reject) => {
-    Services.search.addEngine(url, null, "", false, {
-      onSuccess(engine) { resolve(engine); },
-      onError() { reject(); }
-    });
-  });
+  await withNewSearchEngine(async function(engine) {
+    let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
 
-  let previousEngine = Services.search.currentEngine;
-  Services.search.currentEngine = suggestionEngine;
+    info("Type a query. Suggestions should be generated by the test engine.");
+    let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+    await searchInAwesomebar("query");
+    info("Clicking the urlbar suggestion.");
+    await clickURLBarSuggestion("queryfoo");
+    await p;
 
-  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
+    // Check if the scalars contain the expected values.
+    const scalars = getParentProcessScalars(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN, true, false);
+    checkKeyedScalar(scalars, SCALAR_URLBAR, "search_suggestion", 1);
+    Assert.equal(Object.keys(scalars[SCALAR_URLBAR]).length, 1,
+                "This search must only increment one entry in the scalar.");
 
-  info("Type a query. Suggestions should be generated by the test engine.");
-  let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
-  await searchInAwesomebar("query");
-  info("Clicking the urlbar suggestion.");
-  await clickURLBarSuggestion("queryfoo");
-  await p;
-
-  // Check if the scalars contain the expected values.
-  const scalars = getParentProcessScalars(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN, true, false);
-  checkKeyedScalar(scalars, SCALAR_URLBAR, "search_suggestion", 1);
-  Assert.equal(Object.keys(scalars[SCALAR_URLBAR]).length, 1,
-               "This search must only increment one entry in the scalar.");
+    // Make sure SEARCH_COUNTS contains identical values.
+    let searchEngineId = "other-" + engine.name;
+    checkKeyedHistogram(search_hist, searchEngineId + ".urlbar", 1);
 
-  // Make sure SEARCH_COUNTS contains identical values.
-  let searchEngineId = "other-" + suggestionEngine.name;
-  checkKeyedHistogram(search_hist, searchEngineId + ".urlbar", 1);
+    // Also check events.
+    let events = Services.telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN, false);
+    events = (events.parent || []).filter(e => e[1] == "navigation" && e[2] == "search");
+    checkEvents(events, [["navigation", "search", "urlbar", "suggestion", {engine: searchEngineId}]]);
 
-  // Also check events.
-  let events = Services.telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN, false);
-  events = (events.parent || []).filter(e => e[1] == "navigation" && e[2] == "search");
-  checkEvents(events, [["navigation", "search", "urlbar", "suggestion", {engine: searchEngineId}]]);
-
-  // Check the histograms as well.
-  let resultIndexes = resultIndexHist.snapshot();
-  checkHistogramResults(resultIndexes, 3, "FX_URLBAR_SELECTED_RESULT_INDEX");
+    // Check the histograms as well.
+    let resultIndexes = resultIndexHist.snapshot();
+    checkHistogramResults(resultIndexes, 3, "FX_URLBAR_SELECTED_RESULT_INDEX");
 
-  let resultTypes = resultTypeHist.snapshot();
-  checkHistogramResults(resultTypes,
-    URLBAR_SELECTED_RESULT_TYPES.searchsuggestion,
-    "FX_URLBAR_SELECTED_RESULT_TYPE");
+    let resultTypes = resultTypeHist.snapshot();
+    checkHistogramResults(resultTypes,
+      URLBAR_SELECTED_RESULT_TYPES.searchsuggestion,
+      "FX_URLBAR_SELECTED_RESULT_TYPE");
 
-  let resultIndexByType = resultIndexByTypeHist.snapshot("searchsuggestion");
-  checkHistogramResults(resultIndexByType,
-    3,
-    "FX_URLBAR_SELECTED_RESULT_INDEX_BY_TYPE");
+    let resultIndexByType = resultIndexByTypeHist.snapshot("searchsuggestion");
+    checkHistogramResults(resultIndexByType,
+      3,
+      "FX_URLBAR_SELECTED_RESULT_INDEX_BY_TYPE");
 
-  let resultMethods = resultMethodHist.snapshot();
-  checkHistogramResults(resultMethods,
-    URLBAR_SELECTED_RESULT_METHODS.click,
-    "FX_URLBAR_SELECTED_RESULT_METHOD");
+    let resultMethods = resultMethodHist.snapshot();
+    checkHistogramResults(resultMethods,
+      URLBAR_SELECTED_RESULT_METHODS.click,
+      "FX_URLBAR_SELECTED_RESULT_METHOD");
 
-  Services.search.currentEngine = previousEngine;
-  Services.search.removeEngine(suggestionEngine);
-  BrowserTestUtils.removeTab(tab);
+    BrowserTestUtils.removeTab(tab);
+  });
 });
 
 // Selects and presses the Return (Enter) key on the first suggestion offered by
 // the test search engine.  This only tests the FX_URLBAR_SELECTED_RESULT_METHOD
 // histogram since test_suggestion_click covers everything else.
 add_task(async function test_suggestion_arrowEnterSelection() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
-
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
 
-  // Create an engine to generate search suggestions and add it as default
-  // for this test.
-  const url = getRootDirectory(gTestPath) + "usageTelemetrySearchSuggestions.xml";
-  let suggestionEngine = await new Promise((resolve, reject) => {
-    Services.search.addEngine(url, null, "", false, {
-      onSuccess(engine) { resolve(engine); },
-      onError() { reject(); }
-    });
-  });
-
-  let previousEngine = Services.search.currentEngine;
-  Services.search.currentEngine = suggestionEngine;
-
-  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
+  await withNewSearchEngine(async function() {
+    let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
 
-  info("Type a query. Suggestions should be generated by the test engine.");
-  let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
-  await searchInAwesomebar("query");
-  info("Select the second result and press Return.");
-  EventUtils.synthesizeKey("KEY_ArrowDown");
-  EventUtils.synthesizeKey("KEY_Enter");
-  await p;
+    info("Type a query. Suggestions should be generated by the test engine.");
+    let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+    await searchInAwesomebar("query");
+    info("Select the second result and press Return.");
+    EventUtils.synthesizeKey("KEY_ArrowDown");
+    EventUtils.synthesizeKey("KEY_Enter");
+    await p;
 
-  let resultMethods = resultMethodHist.snapshot();
-  checkHistogramResults(resultMethods,
-    URLBAR_SELECTED_RESULT_METHODS.arrowEnterSelection,
-    "FX_URLBAR_SELECTED_RESULT_METHOD");
+    let resultMethods = resultMethodHist.snapshot();
+    checkHistogramResults(resultMethods,
+      URLBAR_SELECTED_RESULT_METHODS.arrowEnterSelection,
+      "FX_URLBAR_SELECTED_RESULT_METHOD");
 
-  Services.search.currentEngine = previousEngine;
-  Services.search.removeEngine(suggestionEngine);
-  BrowserTestUtils.removeTab(tab);
+    BrowserTestUtils.removeTab(tab);
+  });
 });
 
 // Selects through tab and presses the Return (Enter) key on the first
 // suggestion offered by the test search engine.
 add_task(async function test_suggestion_tabEnterSelection() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
-
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
 
-  // Create an engine to generate search suggestions and add it as default
-  // for this test.
-  const url = getRootDirectory(gTestPath) + "usageTelemetrySearchSuggestions.xml";
-  let suggestionEngine = await new Promise((resolve, reject) => {
-    Services.search.addEngine(url, null, "", false, {
-      onSuccess(engine) { resolve(engine); },
-      onError() { reject(); }
-    });
-  });
-
-  let previousEngine = Services.search.currentEngine;
-  Services.search.currentEngine = suggestionEngine;
-
-  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
+  await withNewSearchEngine(async function() {
+    let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
 
-  info("Type a query. Suggestions should be generated by the test engine.");
-  let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
-  await searchInAwesomebar("query");
-  info("Select the second result and press Return.");
-  EventUtils.synthesizeKey("KEY_Tab");
-  EventUtils.synthesizeKey("KEY_Enter");
-  await p;
+    info("Type a query. Suggestions should be generated by the test engine.");
+    let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+    await searchInAwesomebar("query");
+    info("Select the second result and press Return.");
+    EventUtils.synthesizeKey("KEY_Tab");
+    EventUtils.synthesizeKey("KEY_Enter");
+    await p;
 
-  let resultMethods = resultMethodHist.snapshot();
-  checkHistogramResults(resultMethods,
-    URLBAR_SELECTED_RESULT_METHODS.tabEnterSelection,
-    "FX_URLBAR_SELECTED_RESULT_METHOD");
+    let resultMethods = resultMethodHist.snapshot();
+    checkHistogramResults(resultMethods,
+      URLBAR_SELECTED_RESULT_METHODS.tabEnterSelection,
+      "FX_URLBAR_SELECTED_RESULT_METHOD");
 
-  Services.search.currentEngine = previousEngine;
-  Services.search.removeEngine(suggestionEngine);
-  BrowserTestUtils.removeTab(tab);
+    BrowserTestUtils.removeTab(tab);
+  });
 });
 
 // Selects through code and presses the Return (Enter) key on the first
 // suggestion offered by the test search engine.
 add_task(async function test_suggestion_enterSelection() {
-  // Let's reset the counts.
   Services.telemetry.clearScalars();
-
   let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
 
-  // Create an engine to generate search suggestions and add it as default
-  // for this test.
-  const url = getRootDirectory(gTestPath) + "usageTelemetrySearchSuggestions.xml";
-  let suggestionEngine = await new Promise((resolve, reject) => {
-    Services.search.addEngine(url, null, "", false, {
-      onSuccess(engine) { resolve(engine); },
-      onError() { reject(); }
-    });
+  await withNewSearchEngine(async function() {
+    let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
+
+    info("Type a query. Suggestions should be generated by the test engine.");
+    let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+    await searchInAwesomebar("query");
+    info("Select the second result and press Return.");
+    gURLBar.popup.selectedIndex = 1;
+    EventUtils.synthesizeKey("KEY_Enter");
+    await p;
+
+    let resultMethods = resultMethodHist.snapshot();
+    checkHistogramResults(resultMethods,
+      URLBAR_SELECTED_RESULT_METHODS.enterSelection,
+      "FX_URLBAR_SELECTED_RESULT_METHOD");
+
+    BrowserTestUtils.removeTab(tab);
   });
-
-  let previousEngine = Services.search.currentEngine;
-  Services.search.currentEngine = suggestionEngine;
-
-  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
+});
 
-  info("Type a query. Suggestions should be generated by the test engine.");
-  let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
-  await searchInAwesomebar("query");
-  info("Select the second result and press Return.");
-  gURLBar.popup.selectedIndex = 1;
-  EventUtils.synthesizeKey("KEY_Enter");
-  await p;
+// Selects through mouse right button and press the Return (Enter) key.
+add_task(async function test_suggestion_rightclick() {
+  Services.telemetry.clearScalars();
+  let resultMethodHist = getAndClearHistogram("FX_URLBAR_SELECTED_RESULT_METHOD");
+
+  await withNewSearchEngine(async function() {
+    let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
 
-  let resultMethods = resultMethodHist.snapshot();
-  checkHistogramResults(resultMethods,
-    URLBAR_SELECTED_RESULT_METHODS.enterSelection,
-    "FX_URLBAR_SELECTED_RESULT_METHOD");
+    info("Type a query. Suggestions should be generated by the test engine.");
+    let p = BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+    await searchInAwesomebar("query");
+    info("Right click the the second result and then press Return.");
+    await clickURLBarSuggestion("queryfoo", 2);
+    EventUtils.synthesizeKey("KEY_Enter");
+    await p;
 
-  Services.search.currentEngine = previousEngine;
-  Services.search.removeEngine(suggestionEngine);
-  BrowserTestUtils.removeTab(tab);
+    let resultMethods = resultMethodHist.snapshot();
+    checkHistogramResults(resultMethods,
+      URLBAR_SELECTED_RESULT_METHODS.rightClickEnter,
+      "FX_URLBAR_SELECTED_RESULT_METHOD");
+
+    BrowserTestUtils.removeTab(tab);
+  });
 });

--- a/browser/themes/osx/browser.css
+++ b/browser/themes/osx/browser.css
@@ -330,16 +330,20 @@ html|input.urlbar-input {
 }
 
 .urlbar-display {
   margin-top: 0;
   margin-bottom: 0;
   color: GrayText;
 }
 
+#pageAction-panel-shareURL {
+  list-style-image: url("chrome://browser/skin/share.svg");
+}
+
 %include ../shared/urlbarSearchSuggestionsNotification.inc.css
 
 /* ----- AUTOCOMPLETE ----- */
 
 %include ../shared/autocomplete.inc.css
 %include ../shared/urlbar-autocomplete.inc.css
 
 :root {

--- a/browser/themes/osx/jar.mn
+++ b/browser/themes/osx/jar.mn
@@ -51,16 +51,17 @@ browser.jar:
   skin/classic/browser/places/livemark-item.png             (places/livemark-item.png)
   skin/classic/browser/preferences/alwaysAsk.png            (preferences/alwaysAsk.png)
   skin/classic/browser/preferences/application.png          (preferences/application.png)
   skin/classic/browser/preferences/saveFile.png             (preferences/saveFile.png)
 * skin/classic/browser/preferences/preferences.css          (preferences/preferences.css)
 * skin/classic/browser/preferences/in-content/preferences.css (preferences/in-content/preferences.css)
 * skin/classic/browser/preferences/in-content/dialog.css      (preferences/in-content/dialog.css)
   skin/classic/browser/preferences/applications.css         (preferences/applications.css)
+  skin/classic/browser/share.svg                            (share.svg)
   skin/classic/browser/tabbrowser/tabDragIndicator.png                   (tabbrowser/tabDragIndicator.png)
   skin/classic/browser/tabbrowser/tabDragIndicator@2x.png                (tabbrowser/tabDragIndicator@2x.png)
   skin/classic/browser/e10s-64@2x.png                                  (../shared/e10s-64@2x.png)
 
 [extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
 % override chrome://browser/skin/feeds/audioFeedIcon.png                   chrome://browser/skin/feeds/feedIcon.png
 % override chrome://browser/skin/feeds/audioFeedIcon16.png                 chrome://browser/skin/feeds/feedIcon16.png
 % override chrome://browser/skin/feeds/videoFeedIcon.png                   chrome://browser/skin/feeds/feedIcon.png

new file mode 100644
--- /dev/null
+++ b/browser/themes/osx/share.svg
@@ -0,0 +1,7 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16">
+  <path fill="context-fill" d="M12.707 4.294l-4-4A1 1 0 0 0 8.38.077a.984.984 0 0 0-.246-.05A.938.938 0 0 0 8 0a.938.938 0 0 0-.134.027.984.984 0 0 0-.246.05A1 1 0 0 0 7.291.3l-4 4a1 1 0 0 0 1.416 1.408L7 3.415V11a1 1 0 0 0 2 0V3.415l2.293 2.293a1 1 0 0 0 1.414-1.414z"></path>
+  <path fill="context-fill" d="M14 9a1 1 0 0 0-1 1v3a1 1 0 0 1-1 1H4a1 1 0 0 1-1-1v-3a1 1 0 0 0-2 0v3a3 3 0 0 0 3 3h8a3 3 0 0 0 3-3v-3a1 1 0 0 0-1-1z"></path>
+</svg>

--- a/devtools/client/framework/components/toolbox-tabs.js
+++ b/devtools/client/framework/components/toolbox-tabs.js
@@ -8,16 +8,19 @@ const dom = require("devtools/client/sha
 const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
 const {findDOMNode} = require("devtools/client/shared/vendor/react-dom");
 const {button, div} = dom;
 
 const Menu = require("devtools/client/framework/menu");
 const MenuItem = require("devtools/client/framework/menu-item");
 const ToolboxTab = createFactory(require("devtools/client/framework/components/toolbox-tab"));
 
+// 26px is chevron devtools button width.(i.e. tools-chevronmenu)
+const CHEVRON_BUTTON_WIDTH = 26;
+
 class ToolboxTabs extends Component {
   // See toolbox-toolbar propTypes for details on the props used here.
   static get propTypes() {
     return {
       currentToolId: PropTypes.string,
       focusButton: PropTypes.func,
       focusedButton: PropTypes.string,
       highlightedTools: PropTypes.object,
@@ -27,140 +30,237 @@ class ToolboxTabs extends Component {
       L10N: PropTypes.object,
     };
   }
 
   constructor(props) {
     super(props);
 
     this.state = {
-      overflow: false,
+      // Array of overflowed tool id.
+      overflowedTabIds: [],
     };
 
-    this.addFlowEvents = this.addFlowEvents.bind(this);
-    this.removeFlowEvents = this.removeFlowEvents.bind(this);
-    this.onOverflow = this.onOverflow.bind(this);
-    this.onUnderflow = this.onUnderflow.bind(this);
+    // Map with tool Id and its width size. This lifecycle is out of React's
+    // lifecycle. If a tool is registered, ToolboxTabs will add target tool id
+    // to this map. ToolboxTabs will never remove tool id from this cache.
+    this._cachedToolTabsWidthMap = new Map();
+
+    this._resizeTimerId = null;
+    this.resizeHandler = this.resizeHandler.bind(this);
+  }
+
+  componentDidMount() {
+    window.addEventListener("resize", this.resizeHandler);
+    this.updateCachedToolTabsWidthMap();
+    this.updateOverflowedTabs();
+  }
+
+  componentWillUpdate(nextProps, nextState) {
+    if (this.shouldUpdateToolboxTabs(this.props, nextProps)) {
+      // Force recalculate and render in this cycle if panel definition has
+      // changed or selected tool has changed.
+      nextState.overflowedTabIds = [];
+    }
+  }
+
+  componentDidUpdate(prevProps, prevState) {
+    if (this.shouldUpdateToolboxTabs(prevProps, this.props)) {
+      this.updateCachedToolTabsWidthMap();
+      this.updateOverflowedTabs();
+    }
   }
 
-  componentDidUpdate() {
-    this.addFlowEvents();
+  /**
+   * Check if two array of ids are the same or not.
+   */
+  equalToolIdArray(prevPanels, nextPanels) {
+    if (prevPanels.length !== nextPanels.length) {
+      return false;
+    }
+
+    // Check panel definitions even if both of array size is same.
+    // For example, the case of changing the tab's order.
+    return prevPanels.join("-") === nextPanels.join("-");
   }
 
-  componentWillUnmount() {
-    this.removeFlowEvents();
+  /**
+   * Return true if we should update the overflowed tabs.
+   */
+  shouldUpdateToolboxTabs(prevProps, nextProps) {
+    if (prevProps.currentToolId !== nextProps.currentToolId) {
+      return true;
+    }
+
+    let prevPanels = prevProps.panelDefinitions.map(def => def.id);
+    let nextPanels = nextProps.panelDefinitions.map(def => def.id);
+    return !this.equalToolIdArray(prevPanels, nextPanels);
   }
 
-  addFlowEvents() {
-    this.removeFlowEvents();
-    let node = findDOMNode(this);
-    if (node) {
-      node.addEventListener("overflow", this.onOverflow);
-      node.addEventListener("underflow", this.onUnderflow);
+  /**
+   * Update the Map of tool id and tool tab width.
+   */
+  updateCachedToolTabsWidthMap() {
+    let thisNode = findDOMNode(this);
+    for (let tab of thisNode.querySelectorAll(".devtools-tab")) {
+      let tabId = tab.id.replace("toolbox-tab-", "");
+      if (!this._cachedToolTabsWidthMap.has(tabId)) {
+        let cs = getComputedStyle(tab);
+        this._cachedToolTabsWidthMap.set(tabId, parseInt(cs.width, 10));
+      }
     }
   }
 
-  removeFlowEvents() {
+  /**
+   * Update the overflowed tab array from currently displayed tool tab.
+   * If calculated result is the same as the current overflowed tab array, this
+   * function will not update state.
+   */
+  updateOverflowedTabs() {
     let node = findDOMNode(this);
-    if (node) {
-      node.removeEventListener("overflow", this.onOverflow);
-      node.removeEventListener("underflow", this.onUnderflow);
+    const toolboxWidth = parseInt(getComputedStyle(node).width, 10);
+    let { currentToolId } = this.props;
+    let enabledTabs = this.props.panelDefinitions.map(def => def.id);
+    let sumWidth = 0;
+    let visibleTabs = [];
+
+    for (const id of enabledTabs) {
+      let width = this._cachedToolTabsWidthMap.get(id);
+      sumWidth += width;
+      if (sumWidth <= toolboxWidth) {
+        visibleTabs.push(id);
+      } else {
+        sumWidth = sumWidth - width + CHEVRON_BUTTON_WIDTH;
+
+        // If toolbox can't display the Chevron, remove the last tool tab.
+        if (sumWidth > toolboxWidth) {
+          let removeTabId = visibleTabs.pop();
+          sumWidth -= this._cachedToolTabsWidthMap.get(removeTabId);
+        }
+        break;
+      }
+    }
+
+    // If the selected tab is in overflowed tabs, insert it into a visible
+    // toolbox.
+    if (!visibleTabs.includes(currentToolId) &&
+        enabledTabs.includes(currentToolId)) {
+      let selectedToolWidth = this._cachedToolTabsWidthMap.get(currentToolId);
+      while ((sumWidth + selectedToolWidth) > toolboxWidth &&
+             visibleTabs.length > 0) {
+        let removingToolId  = visibleTabs.pop();
+        let removingToolWidth = this._cachedToolTabsWidthMap.get(removingToolId);
+        sumWidth -= removingToolWidth;
+      }
+      visibleTabs.push(currentToolId);
+    }
+
+    if (visibleTabs.length === 0) {
+      visibleTabs = [enabledTabs[0]];
+    }
+
+    let willOverflowTabs = enabledTabs.filter(id => !visibleTabs.includes(id));
+    if (!this.equalToolIdArray(this.state.overflowedTabIds, willOverflowTabs)) {
+      this.setState({ overflowedTabIds: willOverflowTabs });
     }
   }
 
-  onOverflow() {
-    this.setState({
-      overflow: true
-    });
+  resizeHandler(evt) {
+    window.cancelIdleCallback(this._resizeTimerId);
+    this._resizeTimerId = window.requestIdleCallback(() => {
+      this.updateOverflowedTabs();
+    }, { timeout: 300 });
   }
 
-  onUnderflow() {
-    this.setState({
-      overflow: false
+  /**
+   * Render a button to access overflowed tools, displayed only when the toolbar
+   * presents an overflow.
+   */
+  renderToolsChevronButton() {
+    let {
+      panelDefinitions,
+      selectTool,
+      toolbox,
+      L10N,
+    } = this.props;
+
+    return button({
+      className: "devtools-button tools-chevron-menu",
+      tabIndex: -1,
+      title: L10N.getStr("toolbox.allToolsButton.tooltip"),
+      id: "tools-chevron-menu-button",
+      onClick: ({ target }) => {
+        let menu = new Menu({
+          id: "tools-chevron-menupopup"
+        });
+
+        panelDefinitions.forEach(({id, label}) => {
+          if (this.state.overflowedTabIds.includes(id)) {
+            menu.append(new MenuItem({
+              click: () => {
+                selectTool(id);
+              },
+              id: "tools-chevron-menupopup-" + id,
+              label,
+              type: "checkbox",
+            }));
+          }
+        });
+
+        let rect = target.getBoundingClientRect();
+        let screenX = target.ownerDocument.defaultView.mozInnerScreenX;
+        let screenY = target.ownerDocument.defaultView.mozInnerScreenY;
+
+        // Display the popup below the button.
+        menu.popup(rect.left + screenX, rect.bottom + screenY, toolbox);
+        return menu;
+      },
     });
   }
 
   /**
    * Render all of the tabs, based on the panel definitions and builds out
-   * a toolbox tab for each of them. Will render an all-tabs button if the
+   * a toolbox tab for each of them. Will render the chevron button if the
    * container has an overflow.
    */
   render() {
     let {
       currentToolId,
       focusButton,
       focusedButton,
       highlightedTools,
       panelDefinitions,
       selectTool,
     } = this.props;
 
-    let tabs = panelDefinitions.map(panelDefinition => ToolboxTab({
-      key: panelDefinition.id,
-      currentToolId,
-      focusButton,
-      focusedButton,
-      highlightedTools,
-      panelDefinition,
-      selectTool,
-    }));
+    let tabs = panelDefinitions.map(panelDefinition => {
+      // Don't display overflowed tab.
+      if (!this.state.overflowedTabIds.includes(panelDefinition.id)) {
+        return ToolboxTab({
+          key: panelDefinition.id,
+          currentToolId,
+          focusButton,
+          focusedButton,
+          highlightedTools,
+          panelDefinition,
+          selectTool,
+        });
+      }
+      return null;
+    });
 
-    // A wrapper is needed to get flex sizing correct in XUL.
     return div(
       {
         className: "toolbox-tabs-wrapper"
       },
       div(
         {
           className: "toolbox-tabs"
         },
-        tabs
-      ),
-      this.state.overflow ? renderAllToolsButton(this.props) : null
+        tabs,
+        (this.state.overflowedTabIds.length > 0)
+          ? this.renderToolsChevronButton() : null
+      )
     );
   }
 }
 
 module.exports = ToolboxTabs;
-
-/**
- * Render a button to access all tools, displayed only when the toolbar presents an
- * overflow.
- */
-function renderAllToolsButton(props) {
-  let {
-    currentToolId,
-    panelDefinitions,
-    selectTool,
-    toolbox,
-    L10N,
-  } = props;
-
-  return button({
-    className: "all-tools-menu all-tabs-menu",
-    tabIndex: -1,
-    title: L10N.getStr("toolbox.allToolsButton.tooltip"),
-    onClick: ({ target }) => {
-      let menu = new Menu({
-        id: "all-tools-menupopup"
-      });
-      panelDefinitions.forEach(({id, label}) => {
-        menu.append(new MenuItem({
-          checked: currentToolId === id,
-          click: () => {
-            selectTool(id);
-          },
-          id: "all-tools-menupopup-" + id,
-          label,
-          type: "checkbox",
-        }));
-      });
-
-      let rect = target.getBoundingClientRect();
-      let screenX = target.ownerDocument.defaultView.mozInnerScreenX;
-      let screenY = target.ownerDocument.defaultView.mozInnerScreenY;
-
-      // Display the popup below the button.
-      menu.popup(rect.left + screenX, rect.bottom + screenY, toolbox);
-      return menu;
-    },
-  });
-}

--- a/devtools/client/framework/components/toolbox-toolbar.js
+++ b/devtools/client/framework/components/toolbox-toolbar.js
@@ -2,17 +2,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 "use strict";
 
 const { Component, createFactory } = require("devtools/client/shared/vendor/react");
 const dom = require("devtools/client/shared/vendor/react-dom-factories");
 const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
 const {div, button} = dom;
-const {openTrustedLink} = require("devtools/client/shared/link");
+const {openWebLink} = require("devtools/client/shared/link");
 
 const Menu = require("devtools/client/framework/menu");
 const MenuItem = require("devtools/client/framework/menu-item");
 const ToolboxTab = createFactory(require("devtools/client/framework/components/toolbox-tab"));
 const ToolboxTabs = createFactory(require("devtools/client/framework/components/toolbox-tabs"));
 
 /**
  * This is the overall component for the toolbox toolbar. It is designed to not know how
@@ -172,26 +172,26 @@ function renderToolboxButtons({focusedBu
           onKeyDown(event);
         }
       });
     });
 
   // Add the appropriate separator, if needed.
   let children = renderedButtons;
   if (renderedButtons.length) {
+    if (isStart) {
+      children.push(renderSeparator());
     // For the end group we add a separator *before* the RDM button if it
-    // exists.
-    if (rdmIndex !== -1) {
+    // exists, but only if it is not the only button.
+    } else if (rdmIndex !== -1 && visibleButtons.length > 1) {
       children.splice(
         children.length - 1,
         0,
         renderSeparator()
       );
-    } else {
-      children.push(renderSeparator());
     }
   }
 
   return div({id: `toolbox-buttons-${isStart ? "start" : "end"}`}, ...children);
 }
 
 /**
  * Render a separator.
@@ -389,29 +389,29 @@ function showMeatballMenu(
   }));
 
   if (menu.items.length) {
     menu.append(new MenuItem({ type: "separator" }));
   }
 
   // Getting started
   menu.append(new MenuItem({
-    id: "toolbox-meatball-menu-gettingstarted",
-    label: L10N.getStr("toolbox.meatballMenu.gettingStarted.label"),
+    id: "toolbox-meatball-menu-documentation",
+    label: L10N.getStr("toolbox.meatballMenu.documentation.label"),
     click: () => {
-      openTrustedLink("https://developer.mozilla.org/docs/Tools", toolbox);
+      openWebLink("https://developer.mozilla.org/docs/Tools", toolbox);
     },
   }));
 
   // Give feedback
   menu.append(new MenuItem({
-    id: "toolbox-meatball-menu-feedback",
-    label: L10N.getStr("toolbox.meatballMenu.giveFeedback.label"),
+    id: "toolbox-meatball-menu-community",
+    label: L10N.getStr("toolbox.meatballMenu.community.label"),
     click: () => {
-      openTrustedLink("https://discourse.mozilla.org/c/devtools", toolbox);
+      openWebLink("https://discourse.mozilla.org/c/devtools", toolbox);
     },
   }));
 
   const rect = menuButton.getBoundingClientRect();
   const screenX = menuButton.ownerDocument.defaultView.mozInnerScreenX;
   const screenY = menuButton.ownerDocument.defaultView.mozInnerScreenY;
 
   // Display the popup below the button.

--- a/devtools/client/framework/test/browser.ini
+++ b/devtools/client/framework/test/browser.ini
@@ -108,18 +108,18 @@ skip-if = e10s # Bug 1069044 - destroyIn
 [browser_toolbox_telemetry_close.js]
 [browser_toolbox_textbox_context_menu.js]
 [browser_toolbox_theme.js]
 [browser_toolbox_theme_registration.js]
 [browser_toolbox_toggle.js]
 [browser_toolbox_tool_ready.js]
 [browser_toolbox_tool_remote_reopen.js]
 [browser_toolbox_toolbar_overflow.js]
+[browser_toolbox_toolbar_reorder_by_width.js]
 [browser_toolbox_tools_per_toolbox_registration.js]
-[browser_toolbox_transport_events.js]
 [browser_toolbox_view_source_01.js]
 [browser_toolbox_view_source_02.js]
 [browser_toolbox_view_source_03.js]
 [browser_toolbox_view_source_04.js]
 [browser_toolbox_window_reload_target.js]
 [browser_toolbox_window_shortcuts.js]
 skip-if = os == "mac" && os_version == "10.8" || os == "win" && os_version == "5.1" # Bug 851129 - Re-enable browser_toolbox_window_shortcuts.js test after leaks are fixed
 [browser_toolbox_window_title_changes.js]

--- a/devtools/client/framework/test/browser_toolbox_options.js
+++ b/devtools/client/framework/test/browser_toolbox_options.js
@@ -15,16 +15,17 @@ const {PrefObserver} = require("devtools
 
 add_task(async function() {
   const URL = "data:text/html;charset=utf8,test for dynamically registering " +
               "and unregistering tools";
   registerNewTool();
   let tab = await addTab(URL);
   let target = TargetFactory.forTab(tab);
   toolbox = await gDevTools.showToolbox(target);
+
   doc = toolbox.doc;
   await registerNewPerToolboxTool();
   await testSelectTool();
   await testOptionsShortcut();
   await testOptions();
   await testToggleTools();
 
   // Test that registered WebExtensions becomes entries in the
@@ -424,21 +425,21 @@ function checkUnregistered(toolId, defer
     ok(!doc.getElementById("toolbox-tab-" + toolId),
       "Tab removed for " + toolId);
   } else {
     ok(false, "Something went wrong, " + toolId + " was not unregistered");
   }
   deferred.resolve();
 }
 
-function checkRegistered(toolId, deferred, data) {
+async function checkRegistered(toolId, deferred, data) {
   if (data == toolId) {
     ok(true, "Correct tool added back");
     // checking tab on the toolbox
-    let button = doc.getElementById("toolbox-tab-" + toolId);
+    let button = await lookupButtonForToolId(toolId);
     ok(button, "Tab added back for " + toolId);
   } else {
     ok(false, "Something went wrong, " + toolId + " was not registered");
   }
   deferred.resolve();
 }
 
 function GetPref(name) {
@@ -450,16 +451,36 @@ function GetPref(name) {
       return Services.prefs.getIntPref(name);
     case Services.prefs.PREF_BOOL:
       return Services.prefs.getBoolPref(name);
     default:
       throw new Error("Unknown type");
   }
 }
 
+/**
+ * Find the button from specified toolId.
+ * Generally, button which access to the tool panel is in toolbox or
+ * tools menu(in the Chevron menu).
+ */
+async function lookupButtonForToolId(toolId) {
+  let button = doc.getElementById("toolbox-tab-" + toolId);
+  if (!button) {
+    // search from the tools menu.
+    let menuPopup = await openChevronMenu(toolbox);
+    button = doc.querySelector("#tools-chevron-menupopup-" + toolId);
+
+    info("Closing the tools-chevron-menupopup popup");
+    let onPopupHidden = once(menuPopup, "popuphidden");
+    menuPopup.hidePopup();
+    await onPopupHidden;
+  }
+  return button;
+}
+
 async function cleanup() {
   gDevTools.unregisterTool("test-tool");
   await toolbox.destroy();
   gBrowser.removeCurrentTab();
   for (let pref of modifiedPrefs) {
     Services.prefs.clearUserPref(pref);
   }
   toolbox = doc = panelWin = modifiedPrefs = null;

--- a/devtools/client/framework/test/browser_toolbox_options_disable_buttons.js
+++ b/devtools/client/framework/test/browser_toolbox_options_disable_buttons.js
@@ -1,17 +1,22 @@
 /* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* vim: set ft=javascript ts=2 et sw=2 tw=80: */
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 "use strict";
 
-const TEST_URL = "data:text/html;charset=utf8,test for dynamically " +
-                 "registering and unregistering tools";
+let TEST_URL = "data:text/html;charset=utf8,test for dynamically " +
+               "registering and unregistering tools";
+
+// The frames button is only shown if the page has at least one iframe so we
+// need to add one to the test page.
+TEST_URL += "<iframe src=\"data:text/plain,iframe\"></iframe>";
+
 var doc = null, toolbox = null, panelWin = null, modifiedPrefs = [];
 
 function test() {
   addTab(TEST_URL).then(tab => {
     let target = TargetFactory.forTab(tab);
     gDevTools.showToolbox(target)
       .then(testSelectTool)
       .then(testToggleToolboxButtons)
@@ -55,53 +60,43 @@ function testSelectTool(devtoolsToolbox)
   return deferred.promise;
 }
 
 function testPreferenceAndUIStateIsConsistent() {
   let checkNodes = [...panelWin.document.querySelectorAll(
     "#enabled-toolbox-buttons-box input[type=checkbox]")];
   let toolboxButtonNodes = [...doc.querySelectorAll(".command-button")];
 
-  // The noautohide button is only displayed in the browser toolbox
-  let toolbarButtons = toolbox.toolbarButtons.filter(
-    tool => tool.id != "command-button-noautohide");
-
-  for (let tool of toolbarButtons) {
+  for (let tool of toolbox.toolbarButtons) {
     let isVisible = getBoolPref(tool.visibilityswitch);
 
     let button = toolboxButtonNodes.find(toolboxButton => toolboxButton.id === tool.id);
     is(!!button, isVisible,
       "Button visibility matches pref for " + tool.id);
 
     let check = checkNodes.filter(node => node.id === tool.id)[0];
     is(check.checked, isVisible,
       "Checkbox should be selected based on current pref for " + tool.id);
   }
 }
 
 function testToggleToolboxButtons() {
   let checkNodes = [...panelWin.document.querySelectorAll(
     "#enabled-toolbox-buttons-box input[type=checkbox]")];
 
-  // The noautohide button is only displayed in the browser toolbox, and the element
-  // picker button is not toggleable.
-  let toolbarButtons = toolbox.toolbarButtons.filter(
-    tool => tool.id != "command-button-noautohide");
-
   let visibleToolbarButtons = toolbox.toolbarButtons.filter(tool => tool.isVisible);
 
-  let toolbarButtonNodes = [...doc.querySelectorAll(".command-button")].filter(
-    btn => btn.id != "command-button-noautohide");
+  let toolbarButtonNodes = [...doc.querySelectorAll(".command-button")];
 
-  is(checkNodes.length, toolbarButtons.length,
+  is(checkNodes.length, toolbox.toolbarButtons.length,
     "All of the buttons are toggleable.");
   is(visibleToolbarButtons.length, toolbarButtonNodes.length,
     "All of the DOM buttons are toggleable.");
 
-  for (let tool of toolbarButtons) {
+  for (let tool of toolbox.toolbarButtons) {
     let id = tool.id;
     let matchedCheckboxes = checkNodes.filter(node => node.id === id);
     let matchedButtons = toolbarButtonNodes.filter(button => button.id === id);
     is(matchedCheckboxes.length, 1,
       "There should be a single toggle checkbox for: " + id);
     if (tool.isVisible) {
       is(matchedButtons.length, 1,
         "There should be a DOM button for the visible: " + id);
@@ -112,24 +107,24 @@ function testToggleToolboxButtons() {
         "There should not be a DOM button for the invisible: " + id);
     }
 
     is(matchedCheckboxes[0].nextSibling.textContent, tool.description,
       "The label for checkbox matches the tool definition.");
   }
 
   // Store modified pref names so that they can be cleared on error.
-  for (let tool of toolbarButtons) {
+  for (let tool of toolbox.toolbarButtons) {
     let pref = tool.visibilityswitch;
     modifiedPrefs.push(pref);
   }
 
   // Try checking each checkbox, making sure that it changes the preference
   for (let node of checkNodes) {
-    let tool = toolbarButtons.filter(
+    let tool = toolbox.toolbarButtons.filter(
       commandButton => commandButton.id === node.id)[0];
     let isVisible = getBoolPref(tool.visibilityswitch);
 
     testPreferenceAndUIStateIsConsistent();
     node.click();
     testPreferenceAndUIStateIsConsistent();
 
     let isVisibleAfterClick = getBoolPref(tool.visibilityswitch);

--- a/devtools/client/framework/test/browser_toolbox_toolbar_overflow.js
+++ b/devtools/client/framework/test/browser_toolbox_toolbar_overflow.js
@@ -7,80 +7,67 @@
 
 // Test that a button to access tools hidden by toolbar overflow is displayed when the
 // toolbar starts to present an overflow.
 let { Toolbox } = require("devtools/client/framework/toolbox");
 
 add_task(async function() {
   let tab = await addTab("about:blank");
 
-  info("Open devtools on the Inspector in a separate window");
-  let toolbox = await openToolboxForTab(tab, "inspector", Toolbox.HostType.WINDOW);
+  info("Open devtools on the Inspector in a bottom dock");
+  let toolbox = await openToolboxForTab(tab, "inspector", Toolbox.HostType.BOTTOM);
 
   let hostWindow = toolbox.win.parent;
   let originalWidth = hostWindow.outerWidth;
   let originalHeight = hostWindow.outerHeight;
 
   info("Resize devtools window to a width that should not trigger any overflow");
   let onResize = once(hostWindow, "resize");
-  hostWindow.resizeTo(640, 300);
+  hostWindow.resizeTo(1350, 300);
   await onResize;
+  waitUntil(() => {
+    // Wait for all buttons are displayed.
+    return toolbox.panelDefinitions.length !==
+      toolbox.doc.querySelectorAll(".devtools-tab").length;
+  });
 
-  let allToolsButton = toolbox.doc.querySelector(".all-tools-menu");
-  ok(!allToolsButton, "The all tools button is not displayed");
+  let chevronMenuButton = toolbox.doc.querySelector(".tools-chevron-menu");
+  ok(!chevronMenuButton, "The chevron menu button is not displayed");
 
   info("Resize devtools window to a width that should trigger an overflow");
   onResize = once(hostWindow, "resize");
-  hostWindow.resizeTo(300, 300);
+  hostWindow.resizeTo(800, 300);
   await onResize;
-
-  info("Wait until the all tools button is available");
-  await waitUntil(() => toolbox.doc.querySelector(".all-tools-menu"));
+  waitUntil(() => !toolbox.doc.querySelector(".tools-chevron-menu"));
 
-  allToolsButton = toolbox.doc.querySelector(".all-tools-menu");
-  ok(allToolsButton, "The all tools button is displayed");
+  info("Wait until the chevron menu button is available");
+  await waitUntil(() => toolbox.doc.querySelector(".tools-chevron-menu"));
 
-  info("Open the all-tools-menupopup and verify that the inspector button is checked");
-  let menuPopup = await openAllToolsMenu(toolbox);
+  chevronMenuButton = toolbox.doc.querySelector(".tools-chevron-menu");
+  ok(chevronMenuButton, "The chevron menu button is displayed");
+
+  info("Open the tools-chevron-menupopup and verify that the inspector button is checked");
+  let menuPopup = await openChevronMenu(toolbox);
 
-  let inspectorButton = toolbox.doc.querySelector("#all-tools-menupopup-inspector");
-  ok(inspectorButton, "The inspector button is available");
-  ok(inspectorButton.getAttribute("checked"), "The inspector button is checked");
+  let inspectorButton = toolbox.doc.querySelector("#tools-chevron-menupopup-inspector");
+  ok(!inspectorButton, "The chevron menu doesn't have the inspector button.");
+
+  let consoleButton = toolbox.doc.querySelector("#tools-chevron-menupopup-webconsole");
+  ok(!consoleButton, "The chevron menu doesn't have the console button.");
 
-  let consoleButton = toolbox.doc.querySelector("#all-tools-menupopup-webconsole");
-  ok(consoleButton, "The console button is available");
-  ok(!consoleButton.getAttribute("checked"), "The console button is not checked");
+  let storageButton = toolbox.doc.querySelector("#tools-chevron-menupopup-storage");
+  ok(storageButton, "The chevron menu has the storage button.");
 
-  info("Switch to the webconsole using the all-tools-menupopup popup");
-  let onSelected = toolbox.once("webconsole-selected");
-  consoleButton.click();
+  info("Switch to the performance using the tools-chevron-menupopup popup");
+  let onSelected = toolbox.once("storage-selected");
+  storageButton.click();
   await onSelected;
 
-  info("Closing the all-tools-menupopup popup");
+  info("Closing the tools-chevron-menupopup popup");
   let onPopupHidden = once(menuPopup, "popuphidden");
   menuPopup.hidePopup();
   await onPopupHidden;
 
-  info("Re-open the all-tools-menupopup and verify that the console button is checked");
-  menuPopup = await openAllToolsMenu(toolbox);
-
-  inspectorButton = toolbox.doc.querySelector("#all-tools-menupopup-inspector");
-  ok(!inspectorButton.getAttribute("checked"), "The inspector button is not checked");
-
-  consoleButton = toolbox.doc.querySelector("#all-tools-menupopup-webconsole");
-  ok(consoleButton.getAttribute("checked"), "The console button is checked");
-
   info("Restore the original window size");
+  onResize = once(hostWindow, "resize");
   hostWindow.resizeTo(originalWidth, originalHeight);
+  await onResize;
 });
-
-async function openAllToolsMenu(toolbox) {
-  let allToolsButton = toolbox.doc.querySelector(".all-tools-menu");
-  EventUtils.synthesizeMouseAtCenter(allToolsButton, {}, toolbox.win);
-
-  let menuPopup = toolbox.doc.querySelector("#all-tools-menupopup");
-  ok(menuPopup, "all-tools-menupopup is available");
-
-  info("Waiting for the menu popup to be displayed");
-  await waitUntil(() => menuPopup && menuPopup.state === "open");
-
-  return menuPopup;
-}

new file mode 100644
--- /dev/null
+++ b/devtools/client/framework/test/browser_toolbox_toolbar_reorder_by_width.js
@@ -0,0 +1,106 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// This test will:
+//
+// * Confirm that currently selected button to access tools will not hide due to overflow.
+//   In this case, a button which is located on the left of a currently selected will hide.
+// * Confirm that a button to access tool will hide when registering a new panel.
+//
+// Note that this test is based on the tab ordinal is fixed.
+// i.e. After changed by Bug 1226272, this test might fail.
+
+let { Toolbox } = require("devtools/client/framework/toolbox");
+
+add_task(async function() {
+  let tab = await addTab("about:blank");
+
+  info("Open devtools on the Storage in a sidebar.");
+  let toolbox = await openToolboxForTab(tab, "storage", Toolbox.HostType.BOTTOM);
+
+  info("Waiting for the window to be resized");
+  let {hostWin, originalWidth, originalHeight} = await resizeWindow(toolbox, 800);
+
+  info("Wait until the tools menu button is available");
+  await waitUntil(() => toolbox.doc.querySelector(".tools-chevron-menu"));
+
+  let toolsMenuButton = toolbox.doc.querySelector(".tools-chevron-menu");
+  ok(toolsMenuButton, "The tools menu button is displayed");
+
+  info("Confirm that selected tab is not hidden.");
+  let storageButton = toolbox.doc.querySelector("#toolbox-tab-storage");
+  ok(storageButton, "The storage tab is on toolbox.");
+
+  await resizeWindow(toolbox, originalWidth, originalHeight);
+});
+
+add_task(async function() {
+  let tab = await addTab("about:blank");
+
+  info("Open devtools on the Storage in a sidebar.");
+  let toolbox = await openToolboxForTab(tab, "storage", Toolbox.HostType.BOTTOM);
+
+  info("Resize devtools window to a width that should trigger an overflow");
+  let {hostWin, originalWidth, originalHeight} = await resizeWindow(toolbox, 800);
+
+  info("Regist a new tab");
+  let onRegistered = toolbox.once("tool-registered");
+  gDevTools.registerTool({
+    id: "test-tools",
+    label: "Test Tools",
+    isMenu: true,
+    isTargetSupported: () => true,
+    build: function() {},
+  });
+  await onRegistered;
+
+  info("Open the tools menu button.");
+  let popup = await openChevronMenu(toolbox);
+
+  info("The registered new tool tab should be in the tools menu.");
+  let testToolsButton = toolbox.doc.querySelector("#tools-chevron-menupopup-test-tools");
+  ok(testToolsButton, "The tools menu has a registered new tool button.");
+
+  info("Closing the tools-chevron-menupopup popup");
+  let onPopupHidden = once(popup, "popuphidden");
+  popup.hidePopup();
+  await onPopupHidden;
+
+  info("Unregistering test-tools");
+  let onUnregistered = toolbox.once("tool-unregistered");
+  gDevTools.unregisterTool("test-tools");
+  await onUnregistered;
+
+  info("Open the tools menu button.");
+  popup = await openChevronMenu(toolbox);
+
+  info("An unregistered new tool tab should not be in the tools menu.");
+  testToolsButton = toolbox.doc.querySelector("#tools-chevron-menupopup-test-tools");
+  ok(!testToolsButton, "The tools menu doesn't have a unregistered new tool button.");
+
+  info("Closing the tools-chevron-menupopup popup");
+  onPopupHidden = once(popup, "popuphidden");
+  popup.hidePopup();
+  await onPopupHidden;
+
+  await resizeWindow(toolbox, originalWidth, originalHeight);
+});
+
+async function resizeWindow(toolbox, width, height) {
+  let hostWindow = toolbox.win.parent;
+  let originalWidth = hostWindow.outerWidth;
+  let originalHeight = hostWindow.outerHeight;
+  let toWidth = width || originalWidth;
+  let toHeight = height || originalHeight;
+
+  info("Resize devtools window to a width that should trigger an overflow");
+  let onResize = once(hostWindow, "resize");
+  hostWindow.resizeTo(toWidth, toHeight);
+  await onResize;
+
+  return {hostWindow, originalWidth, originalHeight};
+}

deleted file mode 100644
--- a/devtools/client/framework/test/browser_toolbox_transport_events.js
+++ /dev/null
@@ -1,112 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
-/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
-/* Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/publicdomain/zero/1.0/ */
-
-"use strict";
-
-const { on, off } = require("devtools/shared/event-emitter");
-const { DebuggerClient } = require("devtools/shared/client/debugger-client");
-
-function test() {
-  gDevTools.on("toolbox-created", onToolboxCreated);
-  on(DebuggerClient, "connect", onDebuggerClientConnect);
-
-  addTab("about:blank").then(function() {
-    let target = TargetFactory.forTab(gBrowser.selectedTab);
-    gDevTools.showToolbox(target, "webconsole").then(testResults);
-  });
-}
-
-function testResults(toolbox) {
-  testPackets(sent1, received1);
-  testPackets(sent2, received2);
-
-  cleanUp(toolbox);
-}
-
-function cleanUp(toolbox) {
-  gDevTools.off("toolbox-created", onToolboxCreated);
-  off(DebuggerClient, "connect", onDebuggerClientConnect);
-
-  toolbox.destroy().then(function() {
-    // TODO: fixme.
-    // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
-    setTimeout(() => {
-      gBrowser.removeCurrentTab();
-      executeSoon(function() {
-        finish();
-      });
-    }, 1000);
-  });
-}
-
-function testPackets(sent, received) {
-  ok(sent.length > 0, "There must be at least one sent packet");
-  ok(received.length > 0, "There must be at leaset one received packet");
-
-  if (!sent.length || received.length) {
-    return;
-  }
-
-  let sentPacket = sent[0];
-  let receivedPacket = received[0];
-
-  is(receivedPacket.from, "root",
-    "The first received packet is from the root");
-  is(receivedPacket.applicationType, "browser",
-    "The first received packet has browser type");
-  is(sentPacket.type, "listTabs",
-    "The first sent packet is for list of tabs");
-}
-
-// Listen to the transport object that is associated with the
-// default Toolbox debugger client
-var sent1 = [];
-var received1 = [];
-
-function send1(packet) {
-  sent1.push(packet);
-}
-
-function onPacket1(packet) {
-  received1.push(packet);
-}
-
-function onToolboxCreated(toolbox) {
-  toolbox.target.makeRemote();
-  let client = toolbox.target.client;
-  let transport = client._transport;
-
-  transport.on("send", send1);
-  transport.on("packet", onPacket1);
-
-  client.addOneTimeListener("closed", () => {
-    transport.off("send", send1);
-    transport.off("packet", onPacket1);
-  });
-}
-
-// Listen to all debugger client object protocols.
-var sent2 = [];
-var received2 = [];
-
-function send2(packet) {
-  sent2.push(packet);
-}
-
-function onPacket2(packet) {
-  received2.push(packet);
-}
-
-function onDebuggerClientConnect(client) {
-  let transport = client._transport;
-
-  transport.on("send", send2);
-  transport.on("packet", onPacket2);
-
-  client.addOneTimeListener("closed", () => {
-    transport.off("send", send2);
-    transport.off("packet", onPacket2);
-  });
-}

--- a/devtools/client/framework/test/head.js
+++ b/devtools/client/framework/test/head.js
@@ -242,8 +242,21 @@ DevToolPanel.prototype = {
 
 /**
  * Create a simple devtools test panel that implements the minimum API needed to be
  * registered and opened in the toolbox.
  */
 function createTestPanel(iframeWindow, toolbox) {
   return new DevToolPanel(iframeWindow, toolbox);
 }
+
+async function openChevronMenu(toolbox) {
+  let chevronMenuButton = toolbox.doc.querySelector(".tools-chevron-menu");
+  EventUtils.synthesizeMouseAtCenter(chevronMenuButton, {}, toolbox.win);
+
+  let menuPopup = toolbox.doc.querySelector("#tools-chevron-menupopup");
+  ok(menuPopup, "tools-chevron-menupopup is available");
+
+  info("Waiting for the menu popup to be displayed");
+  await waitUntil(() => menuPopup && menuPopup.state === "open");
+
+  return menuPopup;
+}

--- a/devtools/client/framework/toolbox-options.js
+++ b/devtools/client/framework/toolbox-options.js
@@ -179,17 +179,17 @@ OptionsPanel.prototype = {
 
     let createCommandCheckbox = button => {
       let checkboxLabel = this.panelDoc.createElement("label");
       let checkboxSpanLabel = this.panelDoc.createElement("span");
       checkboxSpanLabel.textContent = button.description;
       let checkboxInput = this.panelDoc.createElement("input");
       checkboxInput.setAttribute("type", "checkbox");
       checkboxInput.setAttribute("id", button.id);
-      if (button.isVisible) {
+      if (Services.prefs.getBoolPref(button.visibilityswitch, true)) {
         checkboxInput.setAttribute("checked", true);
       }
       checkboxInput.addEventListener("change",
         onCheckboxClick.bind(this, checkboxInput));
 
       checkboxLabel.appendChild(checkboxInput);
       checkboxLabel.appendChild(checkboxSpanLabel);
       return checkboxLabel;

--- a/devtools/client/framework/toolbox.js
+++ b/devtools/client/framework/toolbox.js
@@ -761,32 +761,35 @@ Toolbox.prototype = {
    *                       argument, to be called whenever the checked state changes.
    * @property {Function} teardown - Function run on toolbox close to let a chance to
    *                      unregister listeners set when `setup` was called and avoid
    *                      memory leaks. The same arguments than `setup` function are
    *                      passed to `teardown`.
    * @property {Function} isTargetSupported - Function to automatically enable/disable
    *                      the button based on the target. If the target don't support
    *                      the button feature, this method should return false.
+   * @property {Function} isCurrentlyVisible - Function to automatically
+   *                      hide/show the button based on current state.
    * @property {Function} isChecked - Optional function called to known if the button
    *                      is toggled or not. The function should return true when
    *                      the button should be displayed as toggled on.
    */
   _createButtonState: function(options) {
     let isCheckedValue = false;
     const {
       id,
       className,
       description,
       disabled,
       onClick,
       isInStartContainer,
       setup,
       teardown,
       isTargetSupported,
+      isCurrentlyVisible,
       isChecked,
       onKeyDown
     } = options;
     const toolbox = this;
     const button = {
       id,
       className,
       description,
@@ -797,16 +800,17 @@ Toolbox.prototype = {
         }
       },
       onKeyDown(event) {
         if (typeof onKeyDown == "function") {
           onKeyDown(event, toolbox);
         }
       },
       isTargetSupported,
+      isCurrentlyVisible,
       get isChecked() {
         if (typeof isChecked == "function") {
           return isChecked(toolbox);
         }
         return isCheckedValue;
       },
       set isChecked(value) {
         // Note that if options.isChecked is given, this is ignored
@@ -1235,16 +1239,19 @@ Toolbox.prototype = {
   _buildFrameButton() {
     this.frameButton = this._createButtonState({
       id: "command-button-frames",
       description: L10N.getStr("toolbox.frames.tooltip"),
       onClick: this.showFramesMenu,
       isTargetSupported: target => {
         return target.activeTab && target.activeTab.traits.frames;
       },
+      isCurrentlyVisible: () => {
+        return this.frameMap.size > 1;
+      },
       onKeyDown: this.handleKeyDownOnFramesButton
     });
 
     return this.frameButton;
   },
 
   /**
    * Toggle the picker, but also decide whether or not the highlighter should
@@ -1376,26 +1383,33 @@ Toolbox.prototype = {
   },
 
   /**
    * Ensure the visibility of each toolbox button matches the preference value.
    */
   _commandIsVisible: function(button) {
     const {
       isTargetSupported,
+      isCurrentlyVisible,
       visibilityswitch
     } = button;
 
-    let visible = Services.prefs.getBoolPref(visibilityswitch, true);
-
-    if (isTargetSupported) {
-      return visible && isTargetSupported(this.target);
+    if (!Services.prefs.getBoolPref(visibilityswitch, true)) {
+      return false;
+    }
+
+    if (isTargetSupported && !isTargetSupported(this.target)) {
+      return false;
     }
 
-    return visible;
+    if (isCurrentlyVisible && !isCurrentlyVisible()) {
+      return false;
+    }
+
+    return true;
   },
 
   /**
    * Build a panel for a tool definition.
    *
    * @param {string} toolDefinition
    *        Tool definition of the tool to build a tab for.
    */
@@ -2247,20 +2261,16 @@ Toolbox.prototype = {
    *                 id {Number}: frame ID
    *                 url {String}: frame URL
    *                 title {String}: frame title
    *                 destroy {Boolean}: Set to true if destroyed
    *                 parentID {Number}: ID of the parent frame (not set
    *                                    for top level window)
    */
   _updateFrames: function(data) {
-    if (!Services.prefs.getBoolPref("devtools.command-button-frames.enabled")) {
-      return;
-    }
-
     // We may receive this event before the toolbox is ready.
     if (!this.isReady) {
       return;
     }
 
     // Store (synchronize) data about all existing frames on the backend
     if (data.destroyAll) {
       this.frameMap.clear();
@@ -2297,16 +2307,20 @@ Toolbox.prototype = {
     let topFrameSelected = frame ? !frame.parentID : false;
     this._framesButtonChecked = false;
 
     // If non-top level frame is selected the toolbar button is
     // marked as 'checked' indicating that a child frame is active.
     if (!topFrameSelected && this.selectedFrameId) {
       this._framesButtonChecked = false;
     }
+
+    // We may need to hide/show the frames button now.
+    this.frameButton.isVisible = this._commandIsVisible(this.frameButton);
+    this.component.setToolboxButtons(this.toolbarButtons);
   },
 
   /**
    * Returns a 0-based selected frame depth.
    *
    * For example, if the root frame is selected, the returned value is 0.  For a sub-frame
    * of the root document, the returned value is 1, and so on.
    */

--- a/devtools/client/jar.mn
+++ b/devtools/client/jar.mn
@@ -145,16 +145,17 @@ devtools.jar:
     skin/images/command-screenshot.svg (themes/images/command-screenshot.svg)
     skin/images/command-responsivemode.svg (themes/images/command-responsivemode.svg)
     skin/images/command-pick.svg (themes/images/command-pick.svg)
     skin/images/command-pick-accessibility.svg (themes/images/command-pick-accessibility.svg)
     skin/images/command-frames.svg (themes/images/command-frames.svg)
     skin/images/command-eyedropper.svg (themes/images/command-eyedropper.svg)
     skin/images/command-rulers.svg (themes/images/command-rulers.svg)
     skin/images/command-measure.svg (themes/images/command-measure.svg)
+    skin/images/command-chevron.svg (themes/images/command-chevron.svg)
     skin/markup.css (themes/markup.css)
     skin/images/editor-error.png (themes/images/editor-error.png)
     skin/images/breakpoint.svg (themes/images/breakpoint.svg)
     skin/webconsole.css (themes/webconsole.css)
     skin/images/webconsole.svg (themes/images/webconsole.svg)
     skin/images/breadcrumbs-scrollbutton.svg (themes/images/breadcrumbs-scrollbutton.svg)
     skin/animation.css (themes/animation.css)
     skin/animationinspector.css (themes/animationinspector.css)

--- a/devtools/client/locales/en-US/toolbox.properties
+++ b/devtools/client/locales/en-US/toolbox.properties
@@ -168,23 +168,23 @@ toolbox.meatballMenu.hideconsole.label=H
 toolbox.meatballMenu.noautohide.label=Disable popup auto-hide
 
 # LOCALIZATION NOTE (toolbox.meatballMenu.settings.label): This is the label for
 # the item in the "..." menu in the toolbox that brings up the Settings
 # (Options) panel.
 # The keyboard shortcut will be shown to the side of the label.
 toolbox.meatballMenu.settings.label=Settings
 
-# LOCALIZATION NOTE (toolbox.meatballMenu.gettingStarted.label): This is the
-# label for the Getting Started menu item.
-toolbox.meatballMenu.gettingStarted.label=Getting started
+# LOCALIZATION NOTE (toolbox.meatballMenu.documentation.label): This is the
+# label for the Documentation menu item.
+toolbox.meatballMenu.documentation.label=Documentation…
 
-# LOCALIZATION NOTE (toolbox.meatballMenu.giveFeedback.label): This is the label
-# for the Give feedback menu item.
-toolbox.meatballMenu.giveFeedback.label=Give feedback
+# LOCALIZATION NOTE (toolbox.meatballMenu.community.label): This is the label
+# for the Community menu item.
+toolbox.meatballMenu.community.label=Community…
 
 # LOCALIZATION NOTE (toolbox.closebutton.tooltip): This is the tooltip for
 # the close button the developer tools toolbox.
 toolbox.closebutton.tooltip=Close Developer Tools
 
 # LOCALIZATION NOTE (toolbox.allToolsButton.tooltip): This is the tooltip for the
 # "all tools" button displayed when some tools are hidden by overflow of the toolbar.
 toolbox.allToolsButton.tooltip=Select another tool

--- a/devtools/client/themes/common.css
+++ b/devtools/client/themes/common.css
@@ -233,17 +233,17 @@ checkbox:-moz-focusring {
 .devtools-menulist,
 .devtools-toolbarbutton,
 .devtools-button {
   -moz-appearance: none;
   background: transparent;
   border: 1px solid var(--toolbarbutton-border-color);
   border-radius: 2px;
   color: var(--theme-body-color);
-  transition: background 0.05s ease-in-out;
+  transition: background-color 0.05s ease-in-out;
   -moz-box-align: center;
   text-shadow: none;
   padding: 1px;
   margin: 1px;
 
   /* Button text should not wrap on multiple lines */
   white-space: nowrap;
 }
@@ -258,17 +258,16 @@ checkbox:-moz-focusring {
   color: var(--theme-toolbar-color);
   direction: ltr;
   font-size: 11px;
 }
 
 .devtools-button:empty::before {
   content: "";
   display: inline-block;
-  background-size: cover;
   background-repeat: no-repeat;
   vertical-align: middle;
 }
 
 .devtools-button.checked:empty::before {
   color: var(--theme-toolbar-checked-color);
 }
 

new file mode 100644
--- /dev/null
+++ b/devtools/client/themes/images/command-chevron.svg
@@ -0,0 +1,6 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<svg xmlns="http://www.w3.org/2000/svg" width="12" height="12" viewBox="0 0 16 16">
+  <path fill="context-fill" d="M8.707 7.293l-5-5a1 1 0 0 0-1.414 1.414L6.586 8l-4.293 4.293a1 1 0 1 0 1.414 1.414l5-5a1 1 0 0 0 0-1.414zm6 0l-5-5a1 1 0 0 0-1.414 1.414L12.586 8l-4.293 4.293a1 1 0 1 0 1.414 1.414l5-5a1 1 0 0 0 0-1.414z"></path>
+</svg>

--- a/devtools/client/themes/toolbox.css
+++ b/devtools/client/themes/toolbox.css
@@ -11,16 +11,17 @@
   --command-screenshot-image: url(images/command-screenshot.svg);
   --command-responsive-image: url(images/command-responsivemode.svg);
   --command-scratchpad-image: url(images/tool-scratchpad.svg);
   --command-pick-image: url(images/command-pick.svg);
   --command-pick-accessibility-image: url(images/command-pick-accessibility.svg);
   --command-frames-image: url(images/command-frames.svg);
   --command-rulers-image: url(images/command-rulers.svg);
   --command-measure-image: url(images/command-measure.svg);
+  --command-chevron-image: url(images/command-chevron.svg);
 }
 
 /* Toolbox tabbar */
 
 .devtools-tabbar {
   -moz-appearance: none;
   display: flex;
   background: var(--theme-tab-toolbar-background);
@@ -30,18 +31,17 @@
 }
 
 .toolbox-tabs-wrapper {
   position: relative;
   display: flex;
   flex: 1;
 }
 
-.toolbox-tabs-wrapper .all-tools-menu {
-  border-inline-end: 1px solid var(--theme-splitter-color);
+.toolbox-tabs-wrapper .tools-chevron-menu {
   border-top-width: 0;
   border-bottom-width: 0;
 }
 
 .toolbox-tabs {
   position: absolute;
   top: 0;
   left: 0;
@@ -63,56 +63,39 @@
 }
 
 /* Toolbox tabs */
 
 .devtools-tab {
   position: relative;
   display: flex;
   align-items: center;
-  min-width: 32px;
   min-height: 24px;
   margin: 0;
   padding: 0;
   border: none;
   white-space: nowrap;
   overflow: hidden;
   text-overflow: ellipsis;
   background-color: transparent;
+  flex-shrink: 0;
 }
 
 .devtools-tab-label {
   font-size: 12px;
   mask-image: linear-gradient(to left, transparent 0, black 6px);
   /* Set the end padding on the label to make sure the label gets faded out properly */
   padding-inline-end: 10px;
   min-width: 1px;
 }
 
 .devtools-tab-label:-moz-locale-dir(rtl) {
   mask-image: linear-gradient(to right, transparent 0, black 6px);
 }
 
-/* Hide tab icons when the viewport width is limited */
-@media (max-width: 700px) {
-  .devtools-tab-label {
-    /* Set the end padding on the label to make sure the label gets faded out properly */
-    padding-inline-end: 5px;
-  }
-
-  .devtools-tab:not(.devtools-tab-icon-only) {
-    padding-inline-start: 5px !important;
-  }
-
-  /* Hide the icons */
-  .devtools-tab:not(.devtools-tab-icon-only) > img {
-    display: none;
-  }
-}
-
 .devtools-tab-icon-only {
   min-width: 24px;
 }
 
 .devtools-tab {
   color: var(--theme-toolbar-color);
 }
 
@@ -152,18 +135,30 @@
 .devtools-tab.selected > img {
   fill: var(--theme-toolbar-selected-color);
 }
 
 .devtools-tab.highlighted > img {
   fill: var(--theme-toolbar-highlighted-color);
 }
 
+#devtools-chevron-menu-button::before {
+  -moz-context-properties: fill;
+  fill: var(--theme-toolbar-photon-icon-color);
+}
+
 /* Toolbox controls */
 
+#tools-chevron-menu-button::before {
+  top: 0;
+  offset-inline-end: 0;
+  background-image: var(--command-chevron-image);
+  background-position: center;
+}
+
 #toolbox-controls {
   margin-right: 3px;
 }
 
 #toolbox-buttons-end > .devtools-separator {
   margin-inline-start: 5px;
   margin-inline-end: 5px;
 }

--- a/devtools/client/webconsole/new-webconsole.js
+++ b/devtools/client/webconsole/new-webconsole.js
@@ -250,16 +250,17 @@ NewWebConsoleFrame.prototype = {
         Services.scriptloader.loadSubScript(
           "chrome://browser/content/browser-development-helpers.js", this.window);
         shortcuts.on("CmdOrCtrl+Alt+R", this.window.DevelopmentHelpers.quickRestart);
       }
     } else if (Services.prefs.getBoolPref(PREF_SIDEBAR_ENABLED)) {
       shortcuts.on("Esc", event => {
         if (!this.jsterm.autocompletePopup || !this.jsterm.autocompletePopup.isOpen) {
           this.newConsoleOutput.dispatchSidebarClose();
+          this.jsterm.focus();
         }
       });
     }
   },
   /**
    * Handler for page location changes.
    *
    * @param string uri

--- a/devtools/client/webconsole/test/mochitest/browser.ini
+++ b/devtools/client/webconsole/test/mochitest/browser.ini
@@ -260,16 +260,17 @@ subsuite = clipboard
 [browser_webconsole_context_menu_open_url.js]
 [browser_webconsole_context_menu_store_as_global.js]
 [browser_webconsole_csp_ignore_reflected_xss_message.js]
 skip-if = (e10s && debug) || (e10s && os == 'win') # Bug 1221499 enabled these on windows
 [browser_webconsole_csp_violation.js]
 [browser_webconsole_cspro.js]
 [browser_webconsole_document_focus.js]
 [browser_webconsole_duplicate_errors.js]
+[browser_webconsole_error_with_unicode.js]
 [browser_webconsole_errors_after_page_reload.js]
 [browser_webconsole_eval_in_debugger_stackframe.js]
 [browser_webconsole_eval_in_debugger_stackframe2.js]
 [browser_webconsole_execution_scope.js]
 [browser_webconsole_external_script_errors.js]
 [browser_webconsole_file_uri.js]
 skip-if = true #	Bug 1404382
 [browser_webconsole_filter_by_input.js]

--- a/devtools/client/webconsole/test/mochitest/browser_webconsole_close_sidebar.js
+++ b/devtools/client/webconsole/test/mochitest/browser_webconsole_close_sidebar.js
@@ -64,16 +64,18 @@ add_task(async function() {
   await showSidebar(hud);
 
   info("Send escape to hide sidebar");
   onSidebarShown = waitForNodeMutation(wrapper, { childList: true });
   EventUtils.synthesizeKey("KEY_Escape");
   await onSidebarShown;
   sidebar = hud.ui.document.querySelector(".sidebar");
   ok(!sidebar, "Sidebar hidden after sending esc");
+  let inputNode = hud.jsterm.inputNode;
+  ok(hasFocus(inputNode), "console input is focused after closing the sidebar");
 });
 
 async function showSidebar(hud) {
   let onMessage = waitForMessage(hud, "Object");
   ContentTask.spawn(gBrowser.selectedBrowser, {}, function() {
     content.wrappedJSObject.console.log({a: 1});
   });
   await onMessage;

new file mode 100644
--- /dev/null
+++ b/devtools/client/webconsole/test/mochitest/browser_webconsole_error_with_unicode.js
@@ -0,0 +1,24 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Check if an error with Unicode characters is reported correctly.
+
+"use strict";
+
+const TEST_URI = "data:text/html;charset=utf8,<script>\u6e2c</script>";
+const EXPECTED_REPORT = "ReferenceError: \u6e2c is not defined";
+
+add_task(async function() {
+  let hud = await openNewTabAndConsole(TEST_URI);
+
+  // On e10s, the exception is triggered in child process
+  // and is ignored by test harness
+  if (!Services.appinfo.browserTabsRemoteAutostart) {
+    expectUncaughtException();
+  }
+
+  info("generate exception and wait for the message");
+
+  let msg = await waitFor(() => findMessage(hud, EXPECTED_REPORT));
+  ok(msg, `Message found: "${EXPECTED_REPORT}"`);
+});

--- a/devtools/shared/DevToolsUtils.js
+++ b/devtools/shared/DevToolsUtils.js
@@ -352,24 +352,32 @@ exports.isSafeJSObject = function(obj) {
   if (proto && !exports.isSafeJSObject(proto)) {
     return false;
   }
 
   // Allow non-problematic chrome objects.
   return true;
 };
 
+/**
+ * Dump with newline - This is a logging function that will only output when
+ * the preference "devtools.debugger.log" is set to true. Typically it is used
+ * for logging the remote debugging protocol calls.
+ */
 exports.dumpn = function(str) {
   if (flags.wantLogging) {
     dump("DBG-SERVER: " + str + "\n");
   }
 };
 
 /**
- * A verbose logger for low-level tracing.
+ * Dump verbose - This is a verbose logger for low-level tracing, that is typically
+ * used to provide information about the remote debugging protocol's transport
+ * mechanisms. The logging can be enabled by changing the preferences
+ * "devtools.debugger.log" and "devtools.debugger.log.verbose" to true.
  */
 exports.dumpv = function(msg) {
   if (flags.wantVerbose) {
     exports.dumpn(msg);
   }
 };
 
 /**

--- a/devtools/shared/client/debugger-client.js
+++ b/devtools/shared/client/debugger-client.js
@@ -169,21 +169,16 @@ DebuggerClient.prototype = {
    * @return Promise
    *         Resolves once connected with an array whose first element
    *         is the application type, by default "browser", and the second
    *         element is the traits object (help figure out the features
    *         and behaviors of the server we connect to. See RootActor).
    */
   connect: function(onConnected) {
     let deferred = promise.defer();
-    this.emit("connect");
-
-    // Also emit the event on the |DebuggerClient| object (not on the instance),
-    // so it's possible to track all instances.
-    EventEmitter.emit(DebuggerClient, "connect", this);
 
     this.addOneTimeListener("connected", (name, applicationType, traits) => {
       this.traits = traits;
       if (onConnected) {
         onConnected(applicationType, traits);
       }
       deferred.resolve([applicationType, traits]);
     });

--- a/devtools/shared/flags.js
+++ b/devtools/shared/flags.js
@@ -1,18 +1,29 @@
 "use strict";
 
 const Services = require("Services");
 
-/*
- * Create a writable property by tracking it with a private variable.
+/**
+ * This module controls various global flags that can be toggled on and off.
+ * These flags are generally used to change the behavior of the code during
+ * testing. They are tracked by preferences so that they are propagated
+ * between the parent and content processes. The flags are exposed via a module
+ * as a conveniene and to stop from littering preference names throughout the
+ * code ase.
+ *
+ * Each of the flags is documented where it is defined.
+ */
+
+/**
  * We cannot make a normal property writeable on `exports` because
- * the module system freezes it.
+ * the module system freezes it. This function observes a preference
+ * and provides the latest value through a getter.
  */
-function makeWritableFlag(exports, name, pref) {
+function makePrefTrackedFlag(exports, name, pref) {
   let flag;
   // We don't have access to pref in worker, so disable all logs by default
   if (isWorker) {
     flag = false;
   } else {
     flag = Services.prefs.getBoolPref(pref, false);
     let prefObserver = () => {
       flag = Services.prefs.getBoolPref(pref, false);
@@ -28,15 +39,27 @@ function makeWritableFlag(exports, name,
   }
   Object.defineProperty(exports, name, {
     get: function() {
       return flag;
     }
   });
 }
 
-makeWritableFlag(exports, "wantLogging", "devtools.debugger.log");
-makeWritableFlag(exports, "wantVerbose", "devtools.debugger.log.verbose");
+/**
+ * Setting the "devtools.debugger.log" preference to true will enable logging of
+ * the RDP calls to the debugger server.
+ */
+makePrefTrackedFlag(exports, "wantLogging", "devtools.debugger.log");
 
-// When the testing flag is set, various behaviors may be altered from
-// production mode, typically to enable easier testing or enhanced
-// debugging.
-makeWritableFlag(exports, "testing", "devtools.testing");
+/**
+ * Setting the "devtools.debugger.log.verbose" preference to true will enable a
+ * more verbose logging of the the RDP. The "devtools.debugger.log" preference
+ * must be set to true as well for this to have any effect.
+ */
+makePrefTrackedFlag(exports, "wantVerbose", "devtools.debugger.log.verbose");
+
+/**
+ * Setting the "devtools.testing" preference to true will toggle on certain
+ * behaviors that can differ from the production version of the code. These
+ * behaviors typically enable easier testing or enhanced debugging features.
+ */
+makePrefTrackedFlag(exports, "testing", "devtools.testing");

deleted file mode 100644
--- a/devtools/shared/transport/tests/unit/test_transport_events.js
+++ /dev/null
@@ -1,70 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-"use strict";
-
-function run_test() {
-  initTestDebuggerServer();
-
-  add_task(async function() {
-    await test_transport_events("socket", socket_transport);
-    await test_transport_events("local", local_transport);
-    DebuggerServer.destroy();
-  });
-
-  run_next_test();
-}
-
-async function test_transport_events(name, transportFactory) {
-  info(`Started testing of transport: ${name}`);
-
-  Assert.equal(Object.keys(DebuggerServer._connections).length, 0);
-
-  let transport = await transportFactory();
-
-  // Transport expects the hooks to be not null
-  transport.hooks = {
-    onPacket: () => {},
-    onClosed: () => {},
-  };
-
-  let rootReceived = transport.once("packet", packet => {
-    info(`Packet event: ${JSON.stringify(packet)}`);
-    Assert.equal(packet.from, "root");
-  });
-
-  transport.ready();
-  await rootReceived;
-
-  let echoSent = transport.once("send", packet => {
-    info(`Send event: ${JSON.stringify(packet)}`);
-    Assert.equal(packet.to, "root");
-    Assert.equal(packet.type, "echo");
-  });
-
-  let echoReceived = transport.once("packet", packet => {
-    info(`Packet event: ${JSON.stringify(packet)}`);
-    Assert.equal(packet.from, "root");
-    Assert.equal(packet.type, "echo");
-  });
-
-  transport.send({ to: "root", type: "echo" });
-  await echoSent;
-  await echoReceived;
-
-  let clientClosed = transport.once("close", () => {
-    info(`Close event`);
-  });
-
-  let serverClosed = DebuggerServer.once("connectionchange", type => {
-    info(`Server closed`);
-    Assert.equal(type, "closed");
-  });
-
-  transport.close();
-
-  await clientClosed;
-  await serverClosed;
-
-  info(`Finished testing of transport: ${name}`);
-}

--- a/devtools/shared/transport/tests/unit/xpcshell.ini
+++ b/devtools/shared/transport/tests/unit/xpcshell.ini
@@ -12,9 +12,8 @@ support-files =
 [test_client_server_bulk.js]
 [test_dbgsocket.js]
 [test_dbgsocket_connection_drop.js]
 [test_delimited_read.js]
 [test_no_bulk.js]
 [test_packet.js]
 [test_queue.js]
 [test_transport_bulk.js]
-[test_transport_events.js]

--- a/devtools/shared/transport/transport.js
+++ b/devtools/shared/transport/transport.js
@@ -25,17 +25,16 @@
   const DevToolsUtils = require("devtools/shared/DevToolsUtils");
   const { dumpn, dumpv } = DevToolsUtils;
   const flags = require("devtools/shared/flags");
   const StreamUtils = require("devtools/shared/transport/stream-utils");
   const { Packet, JSONPacket, BulkPacket } =
   require("devtools/shared/transport/packets");
   const promise = require("promise");
   const defer = require("devtools/shared/defer");
-  const EventEmitter = require("devtools/shared/event-emitter");
 
   DevToolsUtils.defineLazyGetter(this, "Pipe", () => {
     return CC("@mozilla.org/pipe;1", "nsIPipe", "init");
   });
 
   DevToolsUtils.defineLazyGetter(this, "ScriptableInputStream", () => {
     return CC("@mozilla.org/scriptableinputstream;1",
             "nsIScriptableInputStream", "init");
@@ -96,18 +95,16 @@
    * - onClosed(reason) - called when the connection is closed. |reason| is
    *   an optional nsresult or object, typically passed when the transport is
    *   closed due to some error in a underlying stream.
    *
    * See ./packets.js and the Remote Debugging Protocol specification for more
    * details on the format of these packets.
    */
   function DebuggerTransport(input, output) {
-    EventEmitter.decorate(this);
-
     this._input = input;
     this._scriptableInput = new ScriptableInputStream(input);
     this._output = output;
 
     // The current incoming (possibly partial) header, which will determine which
     // type of Packet |_incoming| below will become.
     this._incomingHeader = "";
     // The current incoming Packet object
@@ -129,18 +126,16 @@
      * Transmit an object as a JSON packet.
      *
      * This method returns immediately, without waiting for the entire
      * packet to be transmitted, registering event handlers as needed to
      * transmit the entire packet. Packets are transmitted in the order
      * they are passed to this method.
      */
     send: function(object) {
-      this.emit("send", object);
-
       let packet = new JSONPacket(this);
       packet.object = object;
       this._outgoing.push(packet);
       this._flushOutgoing();
     },
 
     /**
      * Transmit streaming data via a bulk packet.
@@ -179,34 +174,30 @@
      *                     The stream to copy from.
      *             @return Promise
      *                     The promise is resolved when copying completes or
      *                     rejected if any (unexpected) errors occur.
      *                     This object also emits "progress" events for each chunk
      *                     that is copied.  See stream-utils.js.
      */
     startBulkSend: function(header) {
-      this.emit("startbulksend", header);
-
       let packet = new BulkPacket(this);
       packet.header = header;
       this._outgoing.push(packet);
       this._flushOutgoing();
       return packet.streamReadyForWriting;
     },
 
     /**
      * Close the transport.
      * @param reason nsresult / object (optional)
      *        The status code or error message that corresponds to the reason for
      *        closing the transport (likely because a stream closed or failed).
      */
     close: function(reason) {
-      this.emit("close", reason);
-
       this.active = false;
       this._input.close();
       this._scriptableInput.close();
       this._output.close();
       this._destroyIncoming();
       this._destroyAllOutgoing();
       if (this.hooks) {
         this.hooks.onClosed(reason);
@@ -473,33 +464,31 @@
     /**
      * Handler triggered by an incoming JSONPacket completing it's |read| method.
      * Delivers the packet to this.hooks.onPacket.
      */
     _onJSONObjectReady: function(object) {
       DevToolsUtils.executeSoon(DevToolsUtils.makeInfallible(() => {
       // Ensure the transport is still alive by the time this runs.
         if (this.active) {
-          this.emit("packet", object);
           this.hooks.onPacket(object);
         }
       }, "DebuggerTransport instance's this.hooks.onPacket"));
     },
 
     /**
      * Handler triggered by an incoming BulkPacket entering the |read| phase for
      * the stream portion of the packet.  Delivers info about the incoming
      * streaming data to this.hooks.onBulkPacket.  See the main comment on the
      * transport at the top of this file for more details.
      */
     _onBulkReadReady: function(...args) {
       DevToolsUtils.executeSoon(DevToolsUtils.makeInfallible(() => {
       // Ensure the transport is still alive by the time this runs.
         if (this.active) {
-          this.emit("bulkpacket", ...args);
           this.hooks.onBulkPacket(...args);
         }
       }, "DebuggerTransport instance's this.hooks.onBulkPacket"));
     },
 
     /**
      * Remove all handlers and references related to the current incoming packet,
      * either because it is now complete or because the transport is closing.
@@ -523,35 +512,31 @@
    * connection it merely calls the packet dispatcher of the other side.
    *
    * @param other LocalDebuggerTransport
    *        The other endpoint for this debugger connection.
    *
    * @see DebuggerTransport
    */
   function LocalDebuggerTransport(other) {
-    EventEmitter.decorate(this);
-
     this.other = other;
     this.hooks = null;
 
     // A packet number, shared between this and this.other. This isn't used by the
     // protocol at all, but it makes the packet traces a lot easier to follow.
     this._serial = this.other ? this.other._serial : { count: 0 };
     this.close = this.close.bind(this);
   }
 
   LocalDebuggerTransport.prototype = {
     /**
      * Transmit a message by directly calling the onPacket handler of the other
      * endpoint.
      */
     send: function(packet) {
-      this.emit("send", packet);
-
       let serial = this._serial.count++;
       if (flags.wantLogging) {
         // Check 'from' first, as 'echo' packets have both.
         if (packet.from) {
           dumpn("Packet " + serial + " sent from " + uneval(packet.from));
         } else if (packet.to) {
           dumpn("Packet " + serial + " sent to " + uneval(packet.to));
         }
@@ -560,35 +545,32 @@
       let other = this.other;
       if (other) {
         DevToolsUtils.executeSoon(DevToolsUtils.makeInfallible(() => {
           // Avoid the cost of JSON.stringify() when logging is disabled.
           if (flags.wantLogging) {
             dumpn("Received packet " + serial + ": " + JSON.stringify(packet, null, 2));
           }
           if (other.hooks) {
-            other.emit("packet", packet);
             other.hooks.onPacket(packet);
           }
         }, "LocalDebuggerTransport instance's this.other.hooks.onPacket"));
       }
     },
 
     /**
      * Send a streaming bulk packet directly to the onBulkPacket handler of the
      * other endpoint.
      *
      * This case is much simpler than the full DebuggerTransport, since there is
      * no primary stream we have to worry about managing while we hand it off to
      * others temporarily.  Instead, we can just make a single use pipe and be
      * done with it.
      */
     startBulkSend: function({actor, type, length}) {
-      this.emit("startbulksend", {actor, type, length});
-
       let serial = this._serial.count++;
 
       dumpn("Sent bulk packet " + serial + " for actor " + actor);
       if (!this.other) {
         let error = new Error("startBulkSend: other side of transport missing");
         return promise.reject(error);
       }
 
@@ -611,17 +593,16 @@
             StreamUtils.copyStream(pipe.inputStream, output, length);
             deferred.resolve(copying);
             return copying;
           },
           stream: pipe.inputStream,
           done: deferred
         };
 
-        this.other.emit("bulkpacket", packet);
         this.other.hooks.onBulkPacket(packet);
 
         // Await the result of reading from the stream
         deferred.promise.then(() => pipe.inputStream.close(), this.close);
       }, "LocalDebuggerTransport instance's this.other.hooks.onBulkPacket"));
 
       // Sender
       let sendDeferred = defer();
@@ -648,18 +629,16 @@
 
       return sendDeferred.promise;
     },
 
     /**
      * Close the transport.
      */
     close: function() {
-      this.emit("close");
-
       if (this.other) {
         // Remove the reference to the other endpoint before calling close(), to
         // avoid infinite recursion.
         let other = this.other;
         this.other = null;
         other.close();
       }
       if (this.hooks) {
@@ -707,18 +686,16 @@
    *
    * |prefix| is a string included in the message names, to distinguish
    * multiple servers running in the same child process.
    *
    * This transport exchanges messages named 'debug:<prefix>:packet', where
    * <prefix> is |prefix|, whose data is the protocol packet.
    */
   function ChildDebuggerTransport(mm, prefix) {
-    EventEmitter.decorate(this);
-
     this._mm = mm;
     this._messageName = "debug:" + prefix + ":packet";
   }
 
   /*
    * To avoid confusion, we use 'message' to mean something that
    * nsIMessageSender conveys, and 'packet' to mean a remote debugging
    * protocol packet.
@@ -746,22 +723,20 @@
     },
 
     ready: function() {
       this._addListener();
     },
 
     close: function() {
       this._removeListener();
-      this.emit("close");
       this.hooks.onClosed();
     },
 
     receiveMessage: function({data}) {
-      this.emit("packet", data);
       this.hooks.onPacket(data);
     },
 
     /**
      * Helper method to ensure a given `object` can be sent across message manager
      * without being serialized to JSON.
      * See https://searchfox.org/mozilla-central/rev/6bfadf95b4a6aaa8bb3b2a166d6c3545983e179a/dom/base/nsFrameMessageManager.cpp#458-469
      */
@@ -784,17 +759,16 @@
           }
           return [key];
         }
       }
       return [];
     },
 
     send: function(packet) {
-      this.emit("send", packet);
       if (flags.testing && !this._canBeSerialized(packet)) {
         let attributes = this.pathToUnserializable(packet);
         let msg = "Following packet can't be serialized: " + JSON.stringify(packet);
         msg += "\nBecause of attributes: " + attributes.join(", ") + "\n";
         msg += "Did you pass a function or an XPCOM object in it?";
         throw new Error(msg);
       }
       try {

--- a/docshell/base/nsAboutRedirector.cpp
+++ b/docshell/base/nsAboutRedirector.cpp
@@ -79,21 +79,16 @@ static const RedirEntry kRedirMap[] = {
       nsIAboutModule::ALLOW_SCRIPT |
       nsIAboutModule::HIDE_FROM_ABOUTABOUT
   },
   {
     "networking", "chrome://global/content/aboutNetworking.xhtml",
     nsIAboutModule::ALLOW_SCRIPT
   },
   {
-    "newaddon", "chrome://mozapps/content/extensions/newaddon.xul",
-    nsIAboutModule::ALLOW_SCRIPT |
-      nsIAboutModule::HIDE_FROM_ABOUTABOUT
-  },
-  {
     "performance", "chrome://global/content/aboutPerformance.xhtml",
     nsIAboutModule::ALLOW_SCRIPT
   },
   {
     "plugins", "chrome://global/content/plugins.html",
     nsIAboutModule::URI_MUST_LOAD_IN_CHILD
   },
   {

--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -13685,17 +13685,17 @@ nsDocShell::OnOverLink(nsIContent* aCont
   if (!browserChrome2) {
     browserChrome = do_GetInterface(mTreeOwner);
     if (!browserChrome) {
       return rv;
     }
   }
 
   nsAutoCString spec;
-  rv = aURI->GetSpec(spec);
+  rv = aURI->GetDisplaySpec(spec);
   NS_ENSURE_SUCCESS(rv, rv);
 
   NS_ConvertUTF8toUTF16 uStr(spec);
 
   mozilla::net::PredictorPredict(aURI, mCurrentURI,
                                  nsINetworkPredictor::PREDICT_LINK,
                                  aContent->NodePrincipal()->OriginAttributesRef(),
                                  nullptr);

--- a/docshell/build/nsDocShellModule.cpp
+++ b/docshell/build/nsDocShellModule.cpp
@@ -180,17 +180,16 @@ const mozilla::Module::ContractIDEntry k
 #endif
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "credits", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "license", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "logo", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "memory", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "mozilla", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "neterror", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "networking", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
-  { NS_ABOUT_MODULE_CONTRACTID_PREFIX "newaddon", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "performance", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "plugins", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "serviceworkers", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
 #ifndef ANDROID
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "profiles", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
 #endif
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "srcdoc", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "support", &kNS_ABOUT_REDIRECTOR_MODULE_CID },

--- a/dom/animation/KeyframeUtils.cpp
+++ b/dom/animation/KeyframeUtils.cpp
@@ -43,206 +43,27 @@ namespace mozilla {
 //
 // ------------------------------------------------------------------
 
 // For the aAllowList parameter of AppendStringOrStringSequence and
 // GetPropertyValuesPairs.
 enum class ListAllowance { eDisallow, eAllow };
 
 /**
- * A comparator to sort nsCSSPropertyID values such that longhands are sorted
- * before shorthands, and shorthands with fewer components are sorted before
- * shorthands with more components.
- *
- * Using this allows us to prioritize values specified by longhands (or smaller
- * shorthand subsets) when longhands and shorthands are both specified
- * on the one keyframe.
- *
- * Example orderings that result from this:
- *
- *   margin-left, margin
- *
- * and:
- *
- *   border-top-color, border-color, border-top, border
- */
-class PropertyPriorityComparator
-{
-public:
-  PropertyPriorityComparator()
-    : mSubpropertyCountInitialized(false) {}
-
-  bool Equals(nsCSSPropertyID aLhs, nsCSSPropertyID aRhs) const
-  {
-    return aLhs == aRhs;
-  }
-
-  bool LessThan(nsCSSPropertyID aLhs,
-                nsCSSPropertyID aRhs) const
-  {
-    bool isShorthandLhs = nsCSSProps::IsShorthand(aLhs);
-    bool isShorthandRhs = nsCSSProps::IsShorthand(aRhs);
-
-    if (isShorthandLhs) {
-      if (isShorthandRhs) {
-        // First, sort shorthands by the number of longhands they have.
-        uint32_t subpropCountLhs = SubpropertyCount(aLhs);
-        uint32_t subpropCountRhs = SubpropertyCount(aRhs);
-        if (subpropCountLhs != subpropCountRhs) {
-          return subpropCountLhs < subpropCountRhs;
-        }
-        // Otherwise, sort by IDL name below.
-      } else {
-        // Put longhands before shorthands.
-        return false;
-      }
-    } else {
-      if (isShorthandRhs) {
-        // Put longhands before shorthands.
-        return true;
-      }
-    }
-    // For two longhand properties, or two shorthand with the same number
-    // of longhand components, sort by IDL name.
-    return nsCSSProps::PropertyIDLNameSortPosition(aLhs) <
-           nsCSSProps::PropertyIDLNameSortPosition(aRhs);
-  }
-
-  uint32_t SubpropertyCount(nsCSSPropertyID aProperty) const
-  {
-    if (!mSubpropertyCountInitialized) {
-      PodZero(&mSubpropertyCount);
-      mSubpropertyCountInitialized = true;
-    }
-    if (mSubpropertyCount[aProperty] == 0) {
-      uint32_t count = 0;
-      CSSPROPS_FOR_SHORTHAND_SUBPROPERTIES(
-          p, aProperty, CSSEnabledState::eForAllContent) {
-        ++count;
-      }
-      mSubpropertyCount[aProperty] = count;
-    }
-    return mSubpropertyCount[aProperty];
-  }
-
-private:
-  // Cache of shorthand subproperty counts.
-  mutable RangedArray<
-    uint32_t,
-    eCSSProperty_COUNT_no_shorthands,
-    eCSSProperty_COUNT - eCSSProperty_COUNT_no_shorthands> mSubpropertyCount;
-  mutable bool mSubpropertyCountInitialized;
-};
-
-/**
- * Adaptor for PropertyPriorityComparator to sort objects which have
- * a mProperty member.
- */
-template <typename T>
-class TPropertyPriorityComparator : PropertyPriorityComparator
-{
-public:
-  bool Equals(const T& aLhs, const T& aRhs) const
-  {
-    return PropertyPriorityComparator::Equals(aLhs.mProperty, aRhs.mProperty);
-  }
-  bool LessThan(const T& aLhs, const T& aRhs) const
-  {
-    return PropertyPriorityComparator::LessThan(aLhs.mProperty, aRhs.mProperty);
-  }
-};
-
-/**
- * Iterator to walk through a PropertyValuePair array using the ordering
- * provided by PropertyPriorityComparator.
- */
-class PropertyPriorityIterator
-{
-public:
-  explicit PropertyPriorityIterator(
-    const nsTArray<PropertyValuePair>& aProperties)
-    : mProperties(aProperties)
-  {
-    mSortedPropertyIndices.SetCapacity(mProperties.Length());
-    for (size_t i = 0, len = mProperties.Length(); i < len; ++i) {
-      PropertyAndIndex propertyIndex = { mProperties[i].mProperty, i };
-      mSortedPropertyIndices.AppendElement(propertyIndex);
-    }
-    mSortedPropertyIndices.Sort(PropertyAndIndex::Comparator());
-  }
-
-  class Iter
-  {
-  public:
-    explicit Iter(const PropertyPriorityIterator& aParent)
-      : mParent(aParent)
-      , mIndex(0) { }
-
-    static Iter EndIter(const PropertyPriorityIterator &aParent)
-    {
-      Iter iter(aParent);
-      iter.mIndex = aParent.mSortedPropertyIndices.Length();
-      return iter;
-    }
-
-    bool operator!=(const Iter& aOther) const
-    {
-      return mIndex != aOther.mIndex;
-    }
-
-    Iter& operator++()
-    {
-      MOZ_ASSERT(mIndex + 1 <= mParent.mSortedPropertyIndices.Length(),
-                 "Should not seek past end iterator");
-      mIndex++;
-      return *this;
-    }
-
-    const PropertyValuePair& operator*()
-    {
-      MOZ_ASSERT(mIndex < mParent.mSortedPropertyIndices.Length(),
-                 "Should not try to dereference an end iterator");
-      return mParent.mProperties[mParent.mSortedPropertyIndices[mIndex].mIndex];
-    }
-
-  private:
-    const PropertyPriorityIterator& mParent;
-    size_t mIndex;
-  };
-
-  Iter begin() { return Iter(*this); }
-  Iter end()   { return Iter::EndIter(*this); }
-
-private:
-  struct PropertyAndIndex
-  {
-    nsCSSPropertyID mProperty;
-    size_t mIndex; // Index of mProperty within mProperties
-
-    typedef TPropertyPriorityComparator<PropertyAndIndex> Comparator;
-  };
-
-  const nsTArray<PropertyValuePair>& mProperties;
-  nsTArray<PropertyAndIndex> mSortedPropertyIndices;
-};
-
-/**
  * A property-values pair obtained from the open-ended properties
  * discovered on a regular keyframe or property-indexed keyframe object.
  *
  * Single values (as required by a regular keyframe, and as also supported
  * on property-indexed keyframes) are stored as the only element in
  * mValues.
  */
 struct PropertyValuesPair
 {
   nsCSSPropertyID mProperty;
   nsTArray<nsString> mValues;
-
-  typedef TPropertyPriorityComparator<PropertyValuesPair> Comparator;
 };
 
 /**
  * An additional property (for a property-values pair) found on a
  * BaseKeyframe or BasePropertyIndexedKeyframe object.
  */
 struct AdditionalProperty
 {