--- a/browser/base/content/browser-fullScreenAndPointerLock.js
+++ b/browser/base/content/browser-fullScreenAndPointerLock.js
@@ -251,16 +251,18 @@ var FullScreen = {
     "DOMFullscreen:NewOrigin",
     "DOMFullscreen:Exit",
     "DOMFullscreen:Painted",
   ],
 
   init() {
     // called when we go into full screen, even if initiated by a web page script
     window.addEventListener("fullscreen", this, true);
+    window.addEventListener("willenterfullscreen", this, true);
+    window.addEventListener("willexitfullscreen", this, true);
     window.addEventListener("MozDOMFullscreen:Entered", this,
                             /* useCapture */ true,
                             /* wantsUntrusted */ false);
     window.addEventListener("MozDOMFullscreen:Exited", this,
                             /* useCapture */ true,
                             /* wantsUntrusted */ false);
     for (let type of this._MESSAGES) {
       window.messageManager.addMessageListener(type, this);
@@ -272,16 +274,24 @@ var FullScreen = {
 
   uninit() {
     for (let type of this._MESSAGES) {
       window.messageManager.removeMessageListener(type, this);
     }
     this.cleanup();
   },
 
+  willToggle(aWillEnterFullscreen) {
+    if (aWillEnterFullscreen) {
+      document.documentElement.setAttribute("inFullscreen", true);
+    } else {
+      document.documentElement.removeAttribute("inFullscreen");
+    }
+  },
+
   toggle() {
     var enterFS = window.fullScreen;
 
     // Toggle the View:FullScreen command, which controls elements like the
     // fullscreen menuitem, and menubars.
     let fullscreenCommand = document.getElementById("View:FullScreen");
     if (enterFS) {
       fullscreenCommand.setAttribute("checked", enterFS);
@@ -343,16 +353,22 @@ var FullScreen = {
   },
 
   exitDomFullScreen() {
     document.exitFullscreen();
   },
 
   handleEvent(event) {
     switch (event.type) {
+      case "willenterfullscreen":
+        this.willToggle(true);
+        break;
+      case "willexitfullscreen":
+        this.willToggle(false);
+        break;
       case "fullscreen":
         this.toggle();
         break;
       case "MozDOMFullscreen:Entered": {
         // The event target is the element which requested the DOM
         // fullscreen. If we were entering DOM fullscreen for a remote
         // browser, the target would be `gBrowser` and the original
         // target would be the browser which was the parameter of

--- a/caps/nsScriptSecurityManager.cpp
+++ b/caps/nsScriptSecurityManager.cpp
@@ -160,29 +160,27 @@ inline void SetPendingException(JSContex
 }
 
 // Helper class to get stuff from the ClassInfo and not waste extra time with
 // virtual method calls for things it has already gotten
 class ClassInfoData
 {
 public:
     ClassInfoData(nsIClassInfo *aClassInfo, const char *aName)
-        : mClassInfo(aClassInfo),
-          mFlags(0),
-          mName(const_cast<char *>(aName)),
-          mDidGetFlags(false),
-          mMustFreeName(false)
+      : mClassInfo(aClassInfo),
+        mFlags(0),
+        mName(aName),
+        mDidGetFlags(false)
     {
+      if (!aName) {
+        mName.SetIsVoid(true);
+      }
     }
 
-    ~ClassInfoData()
-    {
-        if (mMustFreeName)
-            free(mName);
-    }
+    ~ClassInfoData() = default;
 
     uint32_t GetFlags()
     {
         if (!mDidGetFlags) {
             if (mClassInfo) {
                 nsresult rv = mClassInfo->GetFlags(&mFlags);
                 if (NS_FAILED(rv)) {
                     mFlags = 0;
@@ -197,39 +195,36 @@ public:
         return mFlags;
     }
 
     bool IsDOMClass()
     {
         return !!(GetFlags() & nsIClassInfo::DOM_OBJECT);
     }
 
-    const char* GetName()
+    void GetName(nsACString& aName)
     {
-        if (!mName) {
+        if (mName.IsVoid()) {
             if (mClassInfo) {
-                mClassInfo->GetClassDescription(&mName);
+                mClassInfo->GetClassDescription(mName);
             }
 
-            if (mName) {
-                mMustFreeName = true;
-            } else {
-                mName = const_cast<char *>("UnnamedClass");
+            if (mName.IsVoid()) {
+                mName.AssignLiteral("UnnamedClass");
             }
         }
 
-        return mName;
+        aName = mName;
     }
 
 private:
     nsIClassInfo *mClassInfo; // WEAK
     uint32_t mFlags;
-    char *mName;
+    nsCString mName;
     bool mDidGetFlags;
-    bool mMustFreeName;
 };
 
 /* static */
 bool
 nsScriptSecurityManager::SecurityCompareURIs(nsIURI* aSourceURI,
                                              nsIURI* aTargetURI)
 {
     return NS_SecurityCompareURIs(aSourceURI, aTargetURI, sStrictFileOriginPolicy);
@@ -1310,32 +1305,34 @@ nsScriptSecurityManager::CanCreateWrappe
 
       nsCOMPtr<nsITreeSelection> treeSelection = do_QueryInterface(aObj);
       if (treeSelection) {
         return NS_OK;
       }
     }
 
     //-- Access denied, report an error
-    nsAutoCString origin;
+    nsAutoCString originUTF8;
     nsIPrincipal* subjectPrincipal = nsContentUtils::SubjectPrincipal();
-    GetPrincipalDomainOrigin(subjectPrincipal, origin);
-    NS_ConvertUTF8toUTF16 originUnicode(origin);
-    NS_ConvertUTF8toUTF16 classInfoName(objClassInfo.GetName());
+    GetPrincipalDomainOrigin(subjectPrincipal, originUTF8);
+    NS_ConvertUTF8toUTF16 originUTF16(originUTF8);
+    nsAutoCString classInfoNameUTF8;
+    objClassInfo.GetName(classInfoNameUTF8);
+    NS_ConvertUTF8toUTF16 classInfoUTF16(classInfoNameUTF8);
     nsresult rv;
     nsAutoString errorMsg;
-    if (originUnicode.IsEmpty()) {
-        const char16_t* formatStrings[] = { classInfoName.get() };
+    if (originUTF16.IsEmpty()) {
+        const char16_t* formatStrings[] = { classInfoUTF16.get() };
         rv = sStrBundle->FormatStringFromName("CreateWrapperDenied",
                                               formatStrings,
                                               1,
                                               errorMsg);
     } else {
-        const char16_t* formatStrings[] = { classInfoName.get(),
-                                            originUnicode.get() };
+        const char16_t* formatStrings[] = { classInfoUTF16.get(),
+                                            originUTF16.get() };
         rv = sStrBundle->FormatStringFromName("CreateWrapperDeniedForOrigin",
                                               formatStrings,
                                               2,
                                               errorMsg);
     }
     NS_ENSURE_SUCCESS(rv, rv);
 
     SetPendingException(cx, errorMsg.get());

--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -120,16 +120,17 @@
 #include "nsCycleCollector.h"
 #include "xpcpublic.h"
 #include "nsIScriptError.h"
 #include "mozilla/Telemetry.h"
 
 #include "mozilla/CORSMode.h"
 
 #include "mozilla/dom/ShadowRoot.h"
+#include "mozilla/dom/HTMLSlotElement.h"
 #include "mozilla/dom/HTMLTemplateElement.h"
 #include "mozilla/dom/SVGUseElement.h"
 
 #include "nsStyledElement.h"
 #include "nsIContentInlines.h"
 #include "nsChildContentList.h"
 
 using namespace mozilla;
@@ -693,16 +694,19 @@ FragmentOrElement::nsDOMSlots::Traverse(
   cb.NoteXPCOMChild(NS_ISUPPORTS_CAST(nsIDOMNodeList*,mExtendedSlots-> mLabelsList));
 
   NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mExtendedSlots->mShadowRoot");
   cb.NoteXPCOMChild(NS_ISUPPORTS_CAST(nsIContent*, mExtendedSlots->mShadowRoot));
 
   NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mExtendedSlots->mContainingShadow");
   cb.NoteXPCOMChild(NS_ISUPPORTS_CAST(nsIContent*, mExtendedSlots->mContainingShadow));
 
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mExtendedSlots->mAssignedSlot");
+  cb.NoteXPCOMChild(NS_ISUPPORTS_CAST(nsIContent*, mExtendedSlots->mAssignedSlot.get()));
+
   NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mExtendedSlots->mXBLBinding");
   cb.NoteNativeChild(mExtendedSlots->mXBLBinding,
                      NS_CYCLE_COLLECTION_PARTICIPANT(nsXBLBinding));
 
   NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mExtendedSlots->mXBLInsertionParent");
   cb.NoteXPCOMChild(mExtendedSlots->mXBLInsertionParent.get());
 
   if (mExtendedSlots->mCustomElementData) {
@@ -740,16 +744,17 @@ FragmentOrElement::nsDOMSlots::Unlink()
     return;
   }
 
   mExtendedSlots->mSMILOverrideStyle = nullptr;
   mExtendedSlots->mControllers = nullptr;
   mExtendedSlots->mLabelsList = nullptr;
   mExtendedSlots->mShadowRoot = nullptr;
   mExtendedSlots->mContainingShadow = nullptr;
+  mExtendedSlots->mAssignedSlot = nullptr;
   MOZ_ASSERT(!(mExtendedSlots->mXBLBinding));
   mExtendedSlots->mXBLInsertionParent = nullptr;
   if (mExtendedSlots->mCustomElementData) {
     if (mExtendedSlots->mCustomElementData->mCustomElementDefinition) {
       mExtendedSlots->mCustomElementData->mCustomElementDefinition = nullptr;
     }
     mExtendedSlots->mCustomElementData = nullptr;
   }
@@ -1210,16 +1215,30 @@ FragmentOrElement::GetExistingDestInsert
 {
   nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
   if (slots) {
     return &slots->mDestInsertionPoints;
   }
   return nullptr;
 }
 
+HTMLSlotElement*
+FragmentOrElement::GetAssignedSlot() const
+{
+  nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
+  return slots ? slots->mAssignedSlot.get() : nullptr;
+}
+
+void
+FragmentOrElement::SetAssignedSlot(HTMLSlotElement* aSlot)
+{
+  nsExtendedDOMSlots* slots = ExtendedDOMSlots();
+  slots->mAssignedSlot = aSlot;
+}
+
 void
 FragmentOrElement::SetXBLInsertionParent(nsIContent* aContent)
 {
   nsCOMPtr<nsIContent> oldInsertionParent = nullptr;
   if (aContent) {
     nsExtendedDOMSlots* slots = ExtendedDOMSlots();
     SetFlags(NODE_MAY_BE_IN_BINDING_MNGR);
     oldInsertionParent = slots->mXBLInsertionParent.forget();

--- a/dom/base/FragmentOrElement.h
+++ b/dom/base/FragmentOrElement.h
@@ -150,16 +150,18 @@ public:
   virtual nsIContent *GetBindingParent() const override;
   virtual nsXBLBinding *GetXBLBinding() const override;
   virtual void SetXBLBinding(nsXBLBinding* aBinding,
                              nsBindingManager* aOldBindingManager = nullptr) override;
   virtual ShadowRoot *GetContainingShadow() const override;
   virtual nsTArray<nsIContent*> &DestInsertionPoints() override;
   virtual nsTArray<nsIContent*> *GetExistingDestInsertionPoints() const override;
   virtual void SetShadowRoot(ShadowRoot* aBinding) override;
+  virtual mozilla::dom::HTMLSlotElement* GetAssignedSlot() const override;
+  virtual void SetAssignedSlot(mozilla::dom::HTMLSlotElement* aSlot) override;
   virtual nsIContent *GetXBLInsertionParent() const override;
   virtual void SetXBLInsertionParent(nsIContent* aContent) override;
   virtual bool IsLink(nsIURI** aURI) const override;
 
   virtual void DestroyContent() override;
   virtual void SaveSubtreeState() override;
 
   NS_IMETHOD WalkContentStyleRules(nsRuleWalker* aRuleWalker) override;
@@ -293,16 +295,21 @@ public:
 
     /**
      * An array of web component insertion points to which this element
      * is distributed.
      */
     nsTArray<nsIContent*> mDestInsertionPoints;
 
     /**
+     * The assigned slot associated with this element.
+     */
+    RefPtr<mozilla::dom::HTMLSlotElement> mAssignedSlot;
+
+    /**
      * XBL binding installed on the element.
      */
     RefPtr<nsXBLBinding> mXBLBinding;
 
     /**
      * XBL binding installed on the lement.
      */
     nsCOMPtr<nsIContent> mXBLInsertionParent;

--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -557,25 +557,24 @@ NS_IMETHODIMP
 nsDOMClassInfo::GetScriptableHelper(nsIXPCScriptable **_retval)
 {
   nsCOMPtr<nsIXPCScriptable> rval = this;
   rval.forget(_retval);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsDOMClassInfo::GetContractID(char **aContractID)
+nsDOMClassInfo::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
-
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsDOMClassInfo::GetClassDescription(char **aClassDescription)
+nsDOMClassInfo::GetClassDescription(nsACString& aClassDescription)
 {
   return GetClassName(aClassDescription);
 }
 
 NS_IMETHODIMP
 nsDOMClassInfo::GetClassID(nsCID **aClassID)
 {
   *aClassID = nullptr;
@@ -594,20 +593,19 @@ nsDOMClassInfo::GetFlags(uint32_t *aFlag
   *aFlags = DOMCLASSINFO_STANDARD_FLAGS;
 
   return NS_OK;
 }
 
 // nsIXPCScriptable
 
 NS_IMETHODIMP
-nsDOMClassInfo::GetClassName(char **aClassName)
+nsDOMClassInfo::GetClassName(nsACString& aClassName)
 {
-  *aClassName = NS_strdup(mData->mClass.name);
-
+  aClassName.Assign(mData->mClass.name);
   return NS_OK;
 }
 
 // virtual
 uint32_t
 nsDOMClassInfo::GetScriptableFlags()
 {
   return mData->mScriptableFlags;

--- a/dom/base/nsGenericDOMDataNode.cpp
+++ b/dom/base/nsGenericDOMDataNode.cpp
@@ -10,16 +10,17 @@
  */
 
 #include "mozilla/DebugOnly.h"
 
 #include "nsGenericDOMDataNode.h"
 #include "mozilla/AsyncEventDispatcher.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLSlotElement.h"
 #include "mozilla/dom/ShadowRoot.h"
 #include "nsIDocument.h"
 #include "nsIDOMDocument.h"
 #include "nsReadableUtils.h"
 #include "mozilla/InternalMutationEvent.h"
 #include "nsIURI.h"
 #include "nsIDOMEvent.h"
 #include "nsIDOMText.h"
@@ -734,16 +735,30 @@ nsGenericDOMDataNode::GetExistingDestIns
 {
   nsDataSlots *slots = GetExistingDataSlots();
   if (slots) {
     return &slots->mDestInsertionPoints;
   }
   return nullptr;
 }
 
+HTMLSlotElement*
+nsGenericDOMDataNode::GetAssignedSlot() const
+{
+  nsDataSlots *slots = GetExistingDataSlots();
+  return slots ? slots->mAssignedSlot.get() : nullptr;
+}
+
+void
+nsGenericDOMDataNode::SetAssignedSlot(HTMLSlotElement* aSlot)
+{
+  nsDataSlots *slots = DataSlots();
+  slots->mAssignedSlot = aSlot;
+}
+
 nsXBLBinding *
 nsGenericDOMDataNode::GetXBLBinding() const
 {
   return nullptr;
 }
 
 void
 nsGenericDOMDataNode::SetXBLBinding(nsXBLBinding* aBinding,
@@ -824,23 +839,27 @@ nsGenericDOMDataNode::nsDataSlots::nsDat
 void
 nsGenericDOMDataNode::nsDataSlots::Traverse(nsCycleCollectionTraversalCallback &cb)
 {
   NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mSlots->mXBLInsertionParent");
   cb.NoteXPCOMChild(mXBLInsertionParent.get());
 
   NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mSlots->mContainingShadow");
   cb.NoteXPCOMChild(NS_ISUPPORTS_CAST(nsIContent*, mContainingShadow));
+
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mSlots->mAssignedSlot");
+  cb.NoteXPCOMChild(NS_ISUPPORTS_CAST(nsIContent*, mAssignedSlot.get()));
 }
 
 void
 nsGenericDOMDataNode::nsDataSlots::Unlink()
 {
   mXBLInsertionParent = nullptr;
   mContainingShadow = nullptr;
+  mAssignedSlot = nullptr;
 }
 
 //----------------------------------------------------------------------
 
 // Implementation of the nsIDOMText interface
 
 nsresult
 nsGenericDOMDataNode::SplitData(uint32_t aOffset, nsIContent** aReturn,

--- a/dom/base/nsGenericDOMDataNode.h
+++ b/dom/base/nsGenericDOMDataNode.h
@@ -21,16 +21,22 @@
 #include "nsCycleCollectionParticipant.h"
 
 #include "nsISMILAttr.h"
 #include "mozilla/dom/ShadowRoot.h"
 
 class nsIDocument;
 class nsIDOMText;
 
+namespace mozilla {
+namespace dom {
+class HTMLSlotElement;
+} // namespace dom
+} // namespace mozilla
+
 #define DATA_NODE_FLAG_BIT(n_) NODE_FLAG_BIT(NODE_TYPE_SPECIFIC_BITS_OFFSET + (n_))
 
 // Data node specific flags
 enum {
   // This bit is set to indicate that if the text node changes to
   // non-whitespace, we may need to create a frame for it. This bit must
   // not be set on nodes that already have a frame.
   NS_CREATE_FRAME_IF_NON_WHITESPACE =     DATA_NODE_FLAG_BIT(0),
@@ -165,16 +171,18 @@ public:
   virtual nsIContent *GetBindingParent() const override;
   virtual nsXBLBinding *GetXBLBinding() const override;
   virtual void SetXBLBinding(nsXBLBinding* aBinding,
                              nsBindingManager* aOldBindingManager = nullptr) override;
   virtual mozilla::dom::ShadowRoot *GetContainingShadow() const override;
   virtual nsTArray<nsIContent*> &DestInsertionPoints() override;
   virtual nsTArray<nsIContent*> *GetExistingDestInsertionPoints() const override;
   virtual void SetShadowRoot(mozilla::dom::ShadowRoot* aShadowRoot) override;
+  virtual mozilla::dom::HTMLSlotElement* GetAssignedSlot() const override;
+  virtual void SetAssignedSlot(mozilla::dom::HTMLSlotElement* aSlot) override;
   virtual nsIContent *GetXBLInsertionParent() const override;
   virtual void SetXBLInsertionParent(nsIContent* aContent) override;
   virtual bool IsNodeOfType(uint32_t aFlags) const override;
   virtual bool IsLink(nsIURI** aURI) const override;
 
   NS_IMETHOD WalkContentStyleRules(nsRuleWalker* aRuleWalker) override;
   NS_IMETHOD_(bool) IsAttributeMapped(const nsAtom* aAttribute) const;
   virtual nsChangeHint GetAttributeChangeHint(const nsAtom* aAttribute,
@@ -278,16 +286,21 @@ protected:
      * @see nsIContent::GetContainingShadow
      */
     RefPtr<mozilla::dom::ShadowRoot> mContainingShadow;
 
     /**
      * @see nsIContent::GetDestInsertionPoints
      */
     nsTArray<nsIContent*> mDestInsertionPoints;
+
+    /**
+     * @see nsIContent::GetAssignedSlot
+     */
+    RefPtr<mozilla::dom::HTMLSlotElement> mAssignedSlot;
   };
 
   // Override from nsINode
   virtual nsINode::nsSlots* CreateSlots() override;
 
   nsDataSlots* DataSlots()
   {
     return static_cast<nsDataSlots*>(Slots());

--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -7304,16 +7304,26 @@ nsGlobalWindow::SetWidgetFullscreen(Full
     // If we enter fullscreen for fullscreen mode, we want
     // the native system behavior.
     aWidget->MakeFullScreenWithNativeTransition(aIsFullscreen, aScreen) :
     aWidget->MakeFullScreen(aIsFullscreen, aScreen);
   return NS_SUCCEEDED(rv);
 }
 
 /* virtual */ void
+nsGlobalWindow::FullscreenWillChange(bool aIsFullscreen)
+{
+  if (aIsFullscreen) {
+    DispatchCustomEvent(NS_LITERAL_STRING("willenterfullscreen"));
+  } else {
+    DispatchCustomEvent(NS_LITERAL_STRING("willexitfullscreen"));
+  }
+}
+
+/* virtual */ void
 nsGlobalWindow::FinishFullscreenChange(bool aIsFullscreen)
 {
   MOZ_ASSERT(IsOuterWindow());
 
   if (aIsFullscreen != mFullScreen) {
     NS_WARNING("Failed to toggle fullscreen state of the widget");
     // We failed to make the widget enter fullscreen.
     // Stop further changes and restore the state.

--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -447,16 +447,17 @@ public:
   void RefreshCompartmentPrincipal();
 
   // For accessing protected field mFullScreen
   friend class FullscreenTransitionTask;
 
   // Outer windows only.
   virtual nsresult SetFullscreenInternal(
     FullscreenReason aReason, bool aIsFullscreen) override final;
+  virtual void FullscreenWillChange(bool aIsFullscreen) override final;
   virtual void FinishFullscreenChange(bool aIsFullscreen) override final;
   bool SetWidgetFullscreen(FullscreenReason aReason, bool aIsFullscreen,
                            nsIWidget* aWidget, nsIScreen* aScreen);
   bool FullScreen() const;
 
   // Inner windows only.
   virtual void SetHasGamepadEventListener(bool aHasGamepad = true) override;
   void NotifyVREventListenerAdded();

--- a/dom/base/nsIContent.h
+++ b/dom/base/nsIContent.h
@@ -23,16 +23,17 @@ class nsIFrame;
 class nsXBLBinding;
 class nsITextControlElement;
 
 namespace mozilla {
 class EventChainPreVisitor;
 struct URLExtraData;
 namespace dom {
 class ShadowRoot;
+class HTMLSlotElement;
 } // namespace dom
 namespace widget {
 struct IMEState;
 } // namespace widget
 } // namespace mozilla
 
 enum nsLinkState {
   eLinkState_Unvisited  = 1,
@@ -739,16 +740,30 @@ public:
   /**
    * Same as DestInsertionPoints except that this method will return
    * null if the array of destination insertion points does not already
    * exist.
    */
   virtual nsTArray<nsIContent*> *GetExistingDestInsertionPoints() const = 0;
 
   /**
+   * Gets the assigned slot associated with this content.
+   *
+   * @return The assigned slot element or null.
+   */
+  virtual mozilla::dom::HTMLSlotElement* GetAssignedSlot() const = 0;
+
+  /**
+   * Sets the assigned slot associated with this content.
+   *
+   * @param aSlot The assigned slot.
+   */
+  virtual void SetAssignedSlot(mozilla::dom::HTMLSlotElement* aSlot) = 0;
+
+  /**
    * Gets the insertion parent element of the XBL binding.
    * The insertion parent is our one true parent in the transformed DOM.
    *
    * @return the insertion parent element.
    */
   virtual nsIContent *GetXBLInsertionParent() const = 0;
 
   /**

--- a/dom/base/nsPIDOMWindow.h
+++ b/dom/base/nsPIDOMWindow.h
@@ -383,16 +383,17 @@ public:
    * Moves the top-level window into fullscreen mode if aIsFullScreen is true,
    * otherwise exits fullscreen.
    *
    * Outer windows only.
    */
   virtual nsresult SetFullscreenInternal(
     FullscreenReason aReason, bool aIsFullscreen) = 0;
 
+  virtual void FullscreenWillChange(bool aIsFullscreen) = 0;
   /**
    * This function should be called when the fullscreen state is flipped.
    * If no widget is involved the fullscreen change, this method is called
    * by SetFullscreenInternal, otherwise, it is called when the widget
    * finishes its change to or from fullscreen.
    *
    * @param aIsFullscreen indicates whether the widget is in fullscreen.
    *

--- a/dom/file/nsHostObjectURI.cpp
+++ b/dom/file/nsHostObjectURI.cpp
@@ -239,28 +239,28 @@ nsHostObjectURI::GetInterfaces(uint32_t 
 NS_IMETHODIMP
 nsHostObjectURI::GetScriptableHelper(nsIXPCScriptable **_retval)
 {
   *_retval = nullptr;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsHostObjectURI::GetContractID(char * *aContractID)
+nsHostObjectURI::GetContractID(nsACString& aContractID)
 {
   // Make sure to modify any subclasses as needed if this ever
   // changes.
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsHostObjectURI::GetClassDescription(char * *aClassDescription)
+nsHostObjectURI::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsHostObjectURI::GetClassID(nsCID * *aClassID)
 {
   // Make sure to modify any subclasses as needed if this ever
   // changes to not call the virtual GetClassIDNoAlloc.

--- a/dom/media/CubebUtils.cpp
+++ b/dom/media/CubebUtils.cpp
@@ -43,16 +43,20 @@
 #define MASK_3F1_LFE    (MASK_3F1 | (1 << AudioConfig::CHANNEL_LFE))
 #define MASK_2F2        (MASK_STEREO | (1 << AudioConfig::CHANNEL_LS) | (1 << AudioConfig::CHANNEL_RS))
 #define MASK_2F2_LFE    (MASK_2F2 | (1 << AudioConfig::CHANNEL_LFE))
 #define MASK_3F2        (MASK_3F | (1 << AudioConfig::CHANNEL_LS) | (1 << AudioConfig::CHANNEL_RS))
 #define MASK_3F2_LFE    (MASK_3F2 | (1 << AudioConfig::CHANNEL_LFE))
 #define MASK_3F3R_LFE   (MASK_3F2_LFE | (1 << AudioConfig::CHANNEL_RCENTER))
 #define MASK_3F4_LFE    (MASK_3F2_LFE | (1 << AudioConfig::CHANNEL_RLS) | (1 << AudioConfig::CHANNEL_RRS))
 
+#if defined(XP_LINUX) && !defined(MOZ_WIDGET_ANDROID)
+#define MOZ_CUBEB_REMOTING
+#endif
+
 extern "C" {
 // These functions are provided by audioipc-server crate
 extern void* audioipc_server_start();
 extern void audioipc_server_stop(void*);
 // These functions are provided by audioipc-client crate
 extern int audioipc_client_init(cubeb**, const char*);
 }
 

--- a/dom/media/MediaPrefs.h
+++ b/dom/media/MediaPrefs.h
@@ -201,19 +201,18 @@ private:
   // Error/warning handling, Decoder Doctor
   DECL_MEDIA_PREF("media.playback.warnings-as-errors",        MediaWarningsAsErrors, bool, false);
   DECL_MEDIA_PREF("media.playback.warnings-as-errors.stagefright-vs-rust",
                                                               MediaWarningsAsErrorsStageFrightVsRust, bool, false);
 
   // resume background video decoding when the cursor is hovering over the tab.
   DECL_MEDIA_PREF("media.resume-bkgnd-video-on-tabhover",     ResumeVideoDecodingOnTabHover, bool, false);
 
-#ifdef MOZ_CUBEB_REMOTING
+  // Enable sandboxing support for cubeb
   DECL_MEDIA_PREF("media.cubeb.sandbox",                      CubebSandbox, bool, false);
-#endif // MOZ_CUBEB_REMOTING
   DECL_MEDIA_PREF("media.videocontrols.lock-video-orientation",  VideoOrientationLockEnabled, bool, false);
 
 public:
   // Manage the singleton:
   static MediaPrefs& GetSingleton();
   static bool SingletonExists();
 
 private:

--- a/dom/webidl/Element.webidl
+++ b/dom/webidl/Element.webidl
@@ -238,16 +238,18 @@ partial interface Element {
 // http://w3c.github.io/webcomponents/spec/shadow/#extensions-to-element-interface
 partial interface Element {
   [Throws,Pref="dom.webcomponents.enabled"]
   ShadowRoot createShadowRoot();
   [Pref="dom.webcomponents.enabled"]
   NodeList getDestinationInsertionPoints();
   [Pref="dom.webcomponents.enabled"]
   readonly attribute ShadowRoot? shadowRoot;
+  [Pref="dom.webcomponents.enabled"]
+  readonly attribute HTMLSlotElement? assignedSlot;
 };
 
 Element implements ChildNode;
 Element implements NonDocumentTypeChildNode;
 Element implements ParentNode;
 Element implements Animatable;
 Element implements GeometryUtils;
 

--- a/dom/webidl/Text.webidl
+++ b/dom/webidl/Text.webidl
@@ -13,9 +13,14 @@
 [Constructor(optional DOMString data = "")]
 interface Text : CharacterData {
   [Throws]
   Text splitText(unsigned long offset);
   [Throws]
   readonly attribute DOMString wholeText;
 };
 
+partial interface Text {
+  [Pref="dom.webcomponents.enabled"]
+  readonly attribute HTMLSlotElement? assignedSlot;
+};
+
 Text implements GeometryUtils;

--- a/gfx/layers/ipc/CrossProcessCompositorBridgeParent.cpp
+++ b/gfx/layers/ipc/CrossProcessCompositorBridgeParent.cpp
@@ -207,28 +207,31 @@ CrossProcessCompositorBridgeParent::Allo
     NS_ERROR("Unexpected layers id in AllocPAPZCTreeManagerParent; dropping message...");
     return nullptr;
   }
 
   MonitorAutoLock lock(*sIndirectLayerTreesLock);
   MOZ_ASSERT(sIndirectLayerTrees.find(layersId) != sIndirectLayerTrees.end());
   MOZ_ASSERT(sIndirectLayerTrees[layersId].mWrBridge == nullptr);
   WebRenderBridgeParent* parent = nullptr;
+  WebRenderBridgeParent* root = nullptr;
   CompositorBridgeParent* cbp = sIndirectLayerTrees[layersId].mParent;
-  if (!cbp) {
+  if (cbp) {
+    root = sIndirectLayerTrees[cbp->RootLayerTreeId()].mWrBridge.get();
+  }
+  if (!root) {
     // This could happen when this function is called after CompositorBridgeParent destruction.
     // This was observed during Tab move between different windows.
     NS_WARNING("Created child without a matching parent?");
     parent = WebRenderBridgeParent::CreateDestroyed(aPipelineId);
     parent->AddRef(); // IPDL reference
     *aIdNamespace = parent->GetIdNamespace();
     *aTextureFactoryIdentifier = TextureFactoryIdentifier(LayersBackend::LAYERS_NONE);
     return parent;
   }
-  WebRenderBridgeParent* root = sIndirectLayerTrees[cbp->RootLayerTreeId()].mWrBridge.get();
 
   RefPtr<wr::WebRenderAPI> api = root->GetWebRenderAPI()->Clone();
   RefPtr<AsyncImagePipelineManager> holder = root->AsyncImageManager();
   RefPtr<CompositorAnimationStorage> animStorage = cbp->GetAnimationStorage();
   parent = new WebRenderBridgeParent(this, aPipelineId, nullptr, root->CompositorScheduler(), Move(api), Move(holder), Move(animStorage));
   parent->AddRef(); // IPDL reference
 
   sIndirectLayerTrees[layersId].mCrossProcessParent = this;

--- a/gfx/layers/wr/WebRenderBridgeChild.cpp
+++ b/gfx/layers/wr/WebRenderBridgeChild.cpp
@@ -8,58 +8,62 @@
 
 #include "gfxPlatform.h"
 #include "mozilla/layers/CompositableClient.h"
 #include "mozilla/layers/CompositorBridgeChild.h"
 #include "mozilla/layers/ImageDataSerializer.h"
 #include "mozilla/layers/IpcResourceUpdateQueue.h"
 #include "mozilla/layers/StackingContextHelper.h"
 #include "mozilla/layers/PTextureChild.h"
+#include "mozilla/layers/WebRenderLayerManager.h"
 #include "mozilla/webrender/WebRenderAPI.h"
 
 namespace mozilla {
 namespace layers {
 
 using namespace mozilla::gfx;
 
 WebRenderBridgeChild::WebRenderBridgeChild(const wr::PipelineId& aPipelineId)
   : mReadLockSequenceNumber(0)
   , mIsInTransaction(false)
   , mIsInClearCachedResources(false)
   , mIdNamespace{0}
   , mResourceId(0)
   , mPipelineId(aPipelineId)
+  , mManager(nullptr)
   , mIPCOpen(false)
   , mDestroyed(false)
   , mFontKeysDeleted(0)
   , mFontInstanceKeysDeleted(0)
 {
 }
 
 void
 WebRenderBridgeChild::Destroy(bool aIsSync)
 {
   if (!IPCOpen()) {
     return;
   }
   // mDestroyed is used to prevent calling Send__delete__() twice.
   // When this function is called from CompositorBridgeChild::Destroy().
   mDestroyed = true;
+  mManager = nullptr;
 
   if (aIsSync) {
     SendShutdownSync();
   } else {
     SendShutdown();
   }
 }
 
 void
 WebRenderBridgeChild::ActorDestroy(ActorDestroyReason why)
 {
   mDestroyed = true;
+  mManager = nullptr;
 }
 
 void
 WebRenderBridgeChild::AddWebRenderParentCommand(const WebRenderParentCommand& aCmd)
 {
   MOZ_ASSERT(mIsInTransaction || mIsInClearCachedResources);
   mParentCommands.AppendElement(aCmd);
 }
@@ -521,23 +525,25 @@ bool
 WebRenderBridgeChild::InForwarderThread()
 {
   return NS_IsMainThread();
 }
 
 mozilla::ipc::IPCResult
 WebRenderBridgeChild::RecvWrUpdated(const wr::IdNamespace& aNewIdNamespace)
 {
+  if (mManager) {
+    mManager->WrUpdated();
+  }
   // Update mIdNamespace to identify obsolete keys and messages by WebRenderBridgeParent.
   // Since usage of invalid keys could cause crash in webrender.
   mIdNamespace = aNewIdNamespace;
   // Just clear FontInstaceKeys/FontKeys, they are removed during WebRenderAPI destruction.
   mFontInstanceKeys.Clear();
   mFontKeys.Clear();
-  GetCompositorBridgeChild()->RecvInvalidateLayers(wr::AsUint64(mPipelineId));
   return IPC_OK();
 }
 
 void
 WebRenderBridgeChild::BeginClearCachedResources()
 {
   mIsInClearCachedResources = true;
 }
@@ -549,16 +555,23 @@ WebRenderBridgeChild::EndClearCachedReso
     mIsInClearCachedResources = false;
     return;
   }
   ProcessWebRenderParentCommands();
   SendClearCachedResources();
   mIsInClearCachedResources = false;
 }
 
+void
+WebRenderBridgeChild::SetWebRenderLayerManager(WebRenderLayerManager* aManager)
+{
+  MOZ_ASSERT(aManager);
+  mManager = aManager;
+}
+
 ipc::IShmemAllocator*
 WebRenderBridgeChild::GetShmemAllocator()
 {
   return static_cast<CompositorBridgeChild*>(Manager());
 }
 
 } // namespace layers
 } // namespace mozilla

--- a/gfx/layers/wr/WebRenderBridgeChild.h
+++ b/gfx/layers/wr/WebRenderBridgeChild.h
@@ -23,16 +23,17 @@ class IpcResourceUpdateQueue;
 }
 
 namespace layers {
 
 class CompositableClient;
 class CompositorBridgeChild;
 class StackingContextHelper;
 class TextureForwarder;
+class WebRenderLayerManager;
 
 template<class T>
 class ThreadSafeWeakPtrHashKey : public PLDHashEntryHdr
 {
 public:
   typedef RefPtr<T> KeyType;
   typedef const T* KeyTypePointer;
 
@@ -136,16 +137,18 @@ public:
   wr::FontInstanceKey GetFontKeyForScaledFont(gfx::ScaledFont* aScaledFont);
 
   void RemoveExpiredFontKeys();
   void ClearReadLocks();
 
   void BeginClearCachedResources();
   void EndClearCachedResources();
 
+  void SetWebRenderLayerManager(WebRenderLayerManager* aManager);
+
   ipc::IShmemAllocator* GetShmemAllocator();
 
 private:
   friend class CompositorBridgeChild;
 
   ~WebRenderBridgeChild() {}
 
   wr::ExternalImageId GetNextExternalImageId();
@@ -194,16 +197,17 @@ private:
   nsDataHashtable<nsUint64HashKey, CompositableClient*> mCompositables;
   nsTArray<nsTArray<ReadLockInit>> mReadLocks;
   uint64_t mReadLockSequenceNumber;
   bool mIsInTransaction;
   bool mIsInClearCachedResources;
   wr::IdNamespace mIdNamespace;
   uint32_t mResourceId;
   wr::PipelineId mPipelineId;
+  WebRenderLayerManager* mManager;
 
   bool mIPCOpen;
   bool mDestroyed;
 
   uint32_t mFontKeysDeleted;
   nsDataHashtable<UnscaledFontHashKey, wr::FontKey> mFontKeys;
 
   uint32_t mFontInstanceKeysDeleted;

--- a/gfx/layers/wr/WebRenderCommandBuilder.cpp
+++ b/gfx/layers/wr/WebRenderCommandBuilder.cpp
@@ -485,17 +485,17 @@ WebRenderCommandBuilder::GenerateFallbac
       if (!lastBounds.IsEqualInterior(clippedBounds)) {
         invalidRegion.OrWith(lastBounds);
         invalidRegion.OrWith(clippedBounds);
       }
     }
     needPaint = !invalidRegion.IsEmpty();
   }
 
-  if (needPaint) {
+  if (needPaint || !fallbackData->GetKey()) {
     gfx::SurfaceFormat format = aItem->GetType() == DisplayItemType::TYPE_MASK ?
                                                       gfx::SurfaceFormat::A8 : gfx::SurfaceFormat::B8G8R8A8;
     if (gfxPrefs::WebRenderBlobImages()) {
       bool snapped;
       bool isOpaque = aItem->GetOpaqueRegion(aDisplayListBuilder, &snapped).Contains(clippedBounds);
 
       RefPtr<gfx::DrawEventRecorderMemory> recorder = MakeAndAddRef<gfx::DrawEventRecorderMemory>();
       RefPtr<gfx::DrawTarget> dummyDt =
@@ -631,10 +631,19 @@ WebRenderCommandBuilder::RemoveUnusedAnd
       iter.Remove();
       continue;
     }
 
     data->SetUsed(false);
   }
 }
 
+void
+WebRenderCommandBuilder::ClearCachedResources()
+{
+  for (auto iter = mWebRenderUserDatas.Iter(); !iter.Done(); iter.Next()) {
+    WebRenderUserData* data = iter.Get()->GetKey();
+    data->ClearCachedResources();
+  }
+}
+
 } // namespace layers
 } // namespace mozilla

--- a/gfx/layers/wr/WebRenderCommandBuilder.h
+++ b/gfx/layers/wr/WebRenderCommandBuilder.h
@@ -89,16 +89,17 @@ public:
   already_AddRefed<WebRenderFallbackData> GenerateFallbackData(nsDisplayItem* aItem,
                                                                wr::DisplayListBuilder& aBuilder,
                                                                wr::IpcResourceUpdateQueue& aResources,
                                                                const StackingContextHelper& aSc,
                                                                nsDisplayListBuilder* aDisplayListBuilder,
                                                                LayoutDeviceRect& aImageRect);
 
   void RemoveUnusedAndResetWebRenderUserData();
+  void ClearCachedResources();
 
   // Those are data that we kept between transactions. We used to cache some
   // data in the layer. But in layers free mode, we don't have layer which
   // means we need some other place to cached the data between transaction.
   // We store the data in frame's property.
   template<class T> already_AddRefed<T>
   CreateOrRecycleWebRenderUserData(nsDisplayItem* aItem,
                                    bool* aOutIsRecycled = nullptr)

--- a/gfx/layers/wr/WebRenderLayerManager.cpp
+++ b/gfx/layers/wr/WebRenderLayerManager.cpp
@@ -65,16 +65,17 @@ WebRenderLayerManager::Initialize(PCompo
     // permission for, or more likely, the GPU process crashed again during
     // reinitialization. We can expect to be notified again to reinitialize
     // (which may or may not be using WebRender).
     gfxCriticalNote << "Failed to create WebRenderBridgeChild.";
     return false;
   }
 
   mWrChild = static_cast<WebRenderBridgeChild*>(bridge);
+  WrBridge()->SetWebRenderLayerManager(this);
   WrBridge()->SendCreate(size.ToUnknownSize());
   WrBridge()->IdentifyTextureHost(textureFactoryIdentifier);
   WrBridge()->SetNamespace(id_namespace);
   *aTextureFactoryIdentifier = textureFactoryIdentifier;
   return true;
 }
 
 void
@@ -496,17 +497,19 @@ WebRenderLayerManager::DidComposite(uint
     nsIWidgetListener *listener = mWidget->GetWidgetListener();
     if (listener) {
       listener->DidCompositeWindow(aTransactionId, aCompositeStart, aCompositeEnd);
     }
     listener = mWidget->GetAttachedWidgetListener();
     if (listener) {
       listener->DidCompositeWindow(aTransactionId, aCompositeStart, aCompositeEnd);
     }
-    mTransactionIdAllocator->NotifyTransactionCompleted(aTransactionId);
+    if (mTransactionIdAllocator) {
+      mTransactionIdAllocator->NotifyTransactionCompleted(aTransactionId);
+    }
   }
 
   // These observers fire whether or not we were in a transaction.
   for (size_t i = 0; i < mDidCompositeObservers.Length(); i++) {
     mDidCompositeObservers[i]->DidComposite();
   }
 }
 
@@ -530,16 +533,23 @@ void
 WebRenderLayerManager::ClearCachedResources(Layer* aSubtree)
 {
   WrBridge()->BeginClearCachedResources();
   DiscardImages();
   WrBridge()->EndClearCachedResources();
 }
 
 void
+WebRenderLayerManager::WrUpdated()
+{
+  mWebRenderCommandBuilder.ClearCachedResources();
+  DiscardLocalImages();
+}
+
+void
 WebRenderLayerManager::UpdateTextureFactoryIdentifier(const TextureFactoryIdentifier& aNewIdentifier,
                                                       uint64_t aDeviceResetSeqNo)
 {
   WrBridge()->IdentifyTextureHost(aNewIdentifier);
 }
 
 TextureFactoryIdentifier
 WebRenderLayerManager::GetTextureFactoryIdentifier()

--- a/gfx/layers/wr/WebRenderLayerManager.h
+++ b/gfx/layers/wr/WebRenderLayerManager.h
@@ -150,16 +150,18 @@ public:
 
   bool SetPendingScrollUpdateForNextTransaction(FrameMetrics::ViewID aScrollId,
                                                 const ScrollUpdateInfo& aUpdateInfo) override;
 
   WebRenderCommandBuilder& CommandBuilder() { return mWebRenderCommandBuilder; }
   WebRenderUserDataRefTable* GetWebRenderUserDataTable() { return mWebRenderCommandBuilder.GetWebRenderUserDataTable(); }
   WebRenderScrollData& GetScrollData() { return mScrollData; }
 
+  void WrUpdated();
+
 private:
   /**
    * Take a snapshot of the parent context, and copy
    * it into mTarget.
    */
   void MakeSnapshotIfRequired(LayoutDeviceIntSize aSize);
 
   void ClearLayer(Layer* aLayer);

--- a/gfx/layers/wr/WebRenderUserData.cpp
+++ b/gfx/layers/wr/WebRenderUserData.cpp
@@ -49,26 +49,35 @@ WebRenderUserData::WrBridge() const
 
 WebRenderImageData::WebRenderImageData(WebRenderLayerManager* aWRManager, nsDisplayItem* aItem)
   : WebRenderUserData(aWRManager, aItem)
 {
 }
 
 WebRenderImageData::~WebRenderImageData()
 {
+  ClearCachedResources();
+}
+
+void
+WebRenderImageData::ClearCachedResources()
+{
   if (mKey) {
     mWRManager->AddImageKeyForDiscard(mKey.value());
+    mKey.reset();
   }
 
   if (mExternalImageId) {
     WrBridge()->DeallocExternalImageId(mExternalImageId.ref());
+    mExternalImageId.reset();
   }
 
   if (mPipelineId) {
     WrBridge()->RemovePipelineIdForCompositable(mPipelineId.ref());
+    mPipelineId.reset();
   }
 }
 
 Maybe<wr::ImageKey>
 WebRenderImageData::UpdateImageKey(ImageContainer* aContainer,
                                    wr::IpcResourceUpdateQueue& aResources,
                                    bool aForceUpdate)
 {
@@ -230,16 +239,25 @@ WebRenderAnimationData::~WebRenderAnimat
 
 WebRenderCanvasData::WebRenderCanvasData(WebRenderLayerManager* aWRManager, nsDisplayItem* aItem)
   : WebRenderUserData(aWRManager, aItem)
 {
 }
 
 WebRenderCanvasData::~WebRenderCanvasData()
 {
+  ClearCachedResources();
+}
+
+void
+WebRenderCanvasData::ClearCachedResources()
+{
+  if (mCanvasRenderer) {
+    mCanvasRenderer->ClearCachedResources();
+  }
 }
 
 WebRenderCanvasRendererAsync*
 WebRenderCanvasData::GetCanvasRenderer()
 {
   if (!mCanvasRenderer) {
     mCanvasRenderer = MakeUnique<WebRenderCanvasRendererAsync>(mWRManager);
   }

--- a/gfx/layers/wr/WebRenderUserData.h
+++ b/gfx/layers/wr/WebRenderUserData.h
@@ -51,17 +51,17 @@ public:
 
   virtual UserDataType GetType() = 0;
   bool IsDataValid(WebRenderLayerManager* aManager);
   bool IsUsed() { return mUsed; }
   void SetUsed(bool aUsed) { mUsed = aUsed; }
   nsIFrame* GetFrame() { return mFrame; }
   uint32_t GetDisplayItemKey() { return mDisplayItemKey; }
   void RemoveFromTable();
-
+  virtual void ClearCachedResources() {};
 protected:
   virtual ~WebRenderUserData();
 
   WebRenderBridgeChild* WrBridge() const;
 
   RefPtr<WebRenderLayerManager> mWRManager;
   nsIFrame* mFrame;
   uint32_t mDisplayItemKey;
@@ -93,17 +93,17 @@ public:
                                          const LayoutDeviceRect& aSCBounds,
                                          const gfx::Matrix4x4& aSCTransform,
                                          const gfx::MaybeIntSize& aScaleToSize,
                                          const wr::ImageRendering& aFilter,
                                          const wr::MixBlendMode& aMixBlendMode,
                                          bool aIsBackfaceVisible);
 
   void CreateImageClientIfNeeded();
-
+  void ClearCachedResources() override;
 protected:
   void CreateExternalImageIfNeeded();
 
   wr::MaybeExternalImageId mExternalImageId;
   Maybe<wr::ImageKey> mKey;
   RefPtr<ImageClient> mImageClient;
   Maybe<wr::PipelineId> mPipelineId;
   RefPtr<ImageContainer> mContainer;
@@ -155,17 +155,17 @@ public:
   explicit WebRenderCanvasData(WebRenderLayerManager* aWRManager, nsDisplayItem* aItem);
   virtual ~WebRenderCanvasData();
 
   virtual WebRenderCanvasData* AsCanvasData() override { return this; }
   virtual UserDataType GetType() override { return UserDataType::eCanvas; }
   static UserDataType Type() { return UserDataType::eCanvas; }
 
   WebRenderCanvasRendererAsync* GetCanvasRenderer();
-
+  void ClearCachedResources() override;
 protected:
   UniquePtr<WebRenderCanvasRendererAsync> mCanvasRenderer;
 };
 
 } // namespace layers
 } // namespace mozilla
 
 #endif /* GFX_WEBRENDERUSERDATA_H */

--- a/gfx/webrender_bindings/RenderD3D11TextureHostOGL.cpp
+++ b/gfx/webrender_bindings/RenderD3D11TextureHostOGL.cpp
@@ -60,16 +60,17 @@ RenderDXGITextureHostOGL::~RenderDXGITex
 
 void
 RenderDXGITextureHostOGL::SetGLContext(gl::GLContext* aContext)
 {
   if (mGL.get() != aContext) {
     // Release the texture handle in the previous gl context.
     DeleteTextureHandle();
     mGL = aContext;
+    mGL->MakeCurrent();
   }
 }
 
 bool
 RenderDXGITextureHostOGL::EnsureLockable()
 {
   if (mTextureHandle[0]) {
     return true;
@@ -286,16 +287,17 @@ RenderDXGIYCbCrTextureHostOGL::~RenderDX
 
 void
 RenderDXGIYCbCrTextureHostOGL::SetGLContext(gl::GLContext* aContext)
 {
   if (mGL.get() != aContext) {
     // Release the texture handle in the previous gl context.
     DeleteTextureHandle();
     mGL = aContext;
+    mGL->MakeCurrent();
   }
 }
 
 bool
 RenderDXGIYCbCrTextureHostOGL::EnsureLockable()
 {
   if (mTextureHandles[0]) {
     return true;

--- a/gfx/webrender_bindings/RenderMacIOSurfaceTextureHostOGL.cpp
+++ b/gfx/webrender_bindings/RenderMacIOSurfaceTextureHostOGL.cpp
@@ -100,16 +100,17 @@ RenderMacIOSurfaceTextureHostOGL::Unlock
 
 void
 RenderMacIOSurfaceTextureHostOGL::SetGLContext(gl::GLContext* aContext)
 {
   if (mGL.get() != aContext) {
     // release the texture handle in the previous gl context
     DeleteTextureHandle();
     mGL = aContext;
+    mGL->MakeCurrent();
   }
 }
 
 void
 RenderMacIOSurfaceTextureHostOGL::DeleteTextureHandle()
 {
   if (mTextureHandles[0] != 0 && mGL && mGL->MakeCurrent()) {
     // Calling glDeleteTextures on 0 isn't an error. So, just make them a single

--- a/js/src/irregexp/RegExpParser.cpp
+++ b/js/src/irregexp/RegExpParser.cpp
@@ -323,16 +323,17 @@ template <typename CharT>
 void
 RegExpParser<CharT>::Advance()
 {
     if (next_pos_ < end_) {
         current_ = *next_pos_;
         next_pos_++;
     } else {
         current_ = kEndMarker;
+        next_pos_ = end_ + 1;
         has_more_ = false;
     }
 }
 
 // Returns the value (0 .. 15) of a hexadecimal character c.
 // If c is not a legal hexadecimal character, returns a value < 0.
 inline int
 HexValue(uint32_t c)

new file mode 100644
--- /dev/null
+++ b/js/src/tests/test262/local/incomplete_hex_unicode_escape.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2015 Zirak. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: An incomplete HexEscape or UnicodeEscape should be treated as an Identity Escape
+info: >
+    An incomplete HexEscape (e.g. /\x/) or UnicodeEscape (/\u/) should fall
+    through to IdentityEscape
+esid: prod-AtomEscape
+---*/
+
+// Hex escape
+assert(/\x/.test("x"), "/\\x/");
+assert(/\xa/.test("xa"), "/\\xa/");
+
+// Unicode escape
+assert(/\u/.test("u"), "/\\u/");
+assert(/\ua/.test("ua"), "/\\ua/");
+
+reportCompare(0, 0);

--- a/js/xpconnect/idl/nsIXPCScriptable.idl
+++ b/js/xpconnect/idl/nsIXPCScriptable.idl
@@ -61,17 +61,17 @@ interface nsIXPConnectWrappedNative;
  * Note: This is not really an XPCOM interface.  For example, callers must
  * guarantee that they set the *_retval of the various methods that return a
  * boolean to PR_TRUE before making the call.  Implementations may skip writing
  * to *_retval unless they want to return PR_FALSE.
  */
 [uuid(19b70b26-7c3f-437f-a04a-2a8f9e28b617)]
 interface nsIXPCScriptable : nsISupports
 {
-    readonly attribute string className;
+    readonly attribute AUTF8String className;
     [notxpcom,nostdcall] uint32_t getScriptableFlags();
     [notxpcom,nostdcall] jsClassPtr getClass();
     [notxpcom,nostdcall] JSClassPtr getJSClass();
 
     void   preCreate(in nsISupports nativeObj, in JSContextPtr cx,
                      in JSObjectPtr globalObj, out JSObjectPtr parentObj);
 
     boolean enumerate(in nsIXPConnectWrappedNative wrapper,

--- a/js/xpconnect/public/xpc_map_end.h
+++ b/js/xpconnect/public/xpc_map_end.h
@@ -18,19 +18,19 @@
 #ifndef XPC_MAP_FLAGS
 #error "Must #define XPC_MAP_FLAGS before #including xpc_map_end.h"
 #endif
 
 #include "js/Id.h"
 
 /**************************************************************/
 
-NS_IMETHODIMP XPC_MAP_CLASSNAME::GetClassName(char * *aClassName)
+NS_IMETHODIMP XPC_MAP_CLASSNAME::GetClassName(nsACString& aClassName)
 {
-    *aClassName = moz_xstrdup(XPC_MAP_QUOTED_CLASSNAME);
+    aClassName.AssignLiteral(XPC_MAP_QUOTED_CLASSNAME);
     return NS_OK;
 }
 
 /**************************************************************/
 
 // virtual
 uint32_t
 XPC_MAP_CLASSNAME::GetScriptableFlags()

--- a/js/xpconnect/src/XPCComponents.cpp
+++ b/js/xpconnect/src/XPCComponents.cpp
@@ -135,26 +135,26 @@ nsXPCComponents_Interfaces::GetInterface
 NS_IMETHODIMP
 nsXPCComponents_Interfaces::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Interfaces::GetContractID(char * *aContractID)
+nsXPCComponents_Interfaces::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Interfaces::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Interfaces::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Interfaces");
+    aClassDescription.AssignLiteral("XPCComponents_Interfaces");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCComponents_Interfaces::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;
@@ -339,26 +339,27 @@ nsXPCComponents_InterfacesByID::GetInter
 NS_IMETHODIMP
 nsXPCComponents_InterfacesByID::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_InterfacesByID::GetContractID(char * *aContractID)
+nsXPCComponents_InterfacesByID::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_InterfacesByID::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_InterfacesByID::GetClassDescription(
+    nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_InterfacesByID");
+    aClassDescription.AssignLiteral("XPCComponents_InterfacesByID");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCComponents_InterfacesByID::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;
@@ -545,26 +546,26 @@ nsXPCComponents_Classes::GetInterfaces(u
 NS_IMETHODIMP
 nsXPCComponents_Classes::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Classes::GetContractID(char * *aContractID)
+nsXPCComponents_Classes::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Classes::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Classes::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Classes");
+    aClassDescription.AssignLiteral("XPCComponents_Classes");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCComponents_Classes::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;
@@ -739,26 +740,26 @@ nsXPCComponents_ClassesByID::GetInterfac
 NS_IMETHODIMP
 nsXPCComponents_ClassesByID::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_ClassesByID::GetContractID(char * *aContractID)
+nsXPCComponents_ClassesByID::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_ClassesByID::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_ClassesByID::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_ClassesByID");
+    aClassDescription.AssignLiteral("XPCComponents_ClassesByID");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCComponents_ClassesByID::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;
@@ -948,26 +949,26 @@ nsXPCComponents_Results::GetInterfaces(u
 NS_IMETHODIMP
 nsXPCComponents_Results::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Results::GetContractID(char * *aContractID)
+nsXPCComponents_Results::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Results::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Results::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Results");
+    aClassDescription.AssignLiteral("XPCComponents_Results");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCComponents_Results::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;
@@ -1117,26 +1118,26 @@ nsXPCComponents_ID::GetInterfaces(uint32
 NS_IMETHODIMP
 nsXPCComponents_ID::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_ID::GetContractID(char * *aContractID)
+nsXPCComponents_ID::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_ID::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_ID::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_ID");
+    aClassDescription.AssignLiteral("XPCComponents_ID");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCComponents_ID::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;
@@ -1293,26 +1294,26 @@ nsXPCComponents_Exception::GetInterfaces
 NS_IMETHODIMP
 nsXPCComponents_Exception::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Exception::GetContractID(char * *aContractID)
+nsXPCComponents_Exception::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Exception::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Exception::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Exception");
+    aClassDescription.AssignLiteral("XPCComponents_Exception");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCComponents_Exception::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;
@@ -1636,26 +1637,26 @@ nsXPCConstructor::GetInterfaces(uint32_t
 NS_IMETHODIMP
 nsXPCConstructor::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCConstructor::GetContractID(char * *aContractID)
+nsXPCConstructor::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCConstructor::GetClassDescription(char * *aClassDescription)
+nsXPCConstructor::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCConstructor");
+    aClassDescription.AssignLiteral("XPCConstructor");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCConstructor::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;
@@ -1837,26 +1838,26 @@ nsXPCComponents_Constructor::GetInterfac
 NS_IMETHODIMP
 nsXPCComponents_Constructor::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     *retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Constructor::GetContractID(char * *aContractID)
+nsXPCComponents_Constructor::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Constructor::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Constructor::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Constructor");
+    aClassDescription.AssignLiteral("XPCComponents_Constructor");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXPCComponents_Constructor::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;

--- a/js/xpconnect/src/XPCRuntimeService.cpp
+++ b/js/xpconnect/src/XPCRuntimeService.cpp
@@ -93,26 +93,26 @@ NS_IMETHODIMP
 BackstagePass::GetScriptableHelper(nsIXPCScriptable** retval)
 {
     nsCOMPtr<nsIXPCScriptable> scriptable = this;
     scriptable.forget(retval);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-BackstagePass::GetContractID(char * *aContractID)
+BackstagePass::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-BackstagePass::GetClassDescription(char * *aClassDescription)
+BackstagePass::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("BackstagePass");
+    aClassDescription.AssignLiteral("BackstagePass");
     return NS_OK;
 }
 
 NS_IMETHODIMP
 BackstagePass::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;

--- a/layout/generic/BlockReflowInput.cpp
+++ b/layout/generic/BlockReflowInput.cpp
@@ -711,16 +711,18 @@ FloatMarginISize(const ReflowInput& aCBR
            ConvertTo(cbwm, wm).ISize(cbwm) +
          aFloatOffsetState.ComputedLogicalBorderPadding().Size(wm).
            ConvertTo(cbwm, wm).ISize(cbwm);
 }
 
 bool
 BlockReflowInput::FlowAndPlaceFloat(nsIFrame* aFloat)
 {
+  MOZ_ASSERT(aFloat->GetParent() == mBlock);
+
   WritingMode wm = mReflowInput.GetWritingMode();
   // Save away the Y coordinate before placing the float. We will
   // restore mBCoord at the end after placing the float. This is
   // necessary because any adjustments to mBCoord during the float
   // placement are for the float only, not for any non-floating
   // content.
   AutoRestore<nscoord> restoreBCoord(mBCoord);
 

--- a/layout/generic/nsInlineFrame.cpp
+++ b/layout/generic/nsInlineFrame.cpp
@@ -323,18 +323,16 @@ nsInlineFrame::Reflow(nsPresContext*    
     return;
   }
   if (IsFrameTreeTooDeep(aReflowInput, aMetrics, aStatus)) {
     return;
   }
 
   bool    lazilySetParentPointer = false;
 
-  nsIFrame* lineContainer = aReflowInput.mLineLayout->LineContainerFrame();
-
    // Check for an overflow list with our prev-in-flow
   nsInlineFrame* prevInFlow = (nsInlineFrame*)GetPrevInFlow();
   if (prevInFlow) {
     AutoFrameListPtr prevOverflowFrames(aPresContext,
                                         prevInFlow->StealOverflowFrames());
     if (prevOverflowFrames) {
       // When pushing and pulling frames we need to check for whether any
       // views need to be reparented.
@@ -350,22 +348,16 @@ nsInlineFrame::Reflow(nsPresContext*    
           !GetNextInFlow()) {
         // If our child list is empty, just put the new frames into it.
         // Note that we don't set the parent pointer for the new frames. Instead wait
         // to do this until we actually reflow the frame. If the overflow list contains
         // thousands of frames this is a big performance issue (see bug #5588)
         mFrames.SetFrames(*prevOverflowFrames);
         lazilySetParentPointer = true;
       } else {
-        // Assign all floats to our block if necessary
-        if (lineContainer && lineContainer->GetPrevContinuation()) {
-          ReparentFloatsForInlineChild(lineContainer,
-                                       prevOverflowFrames->FirstChild(),
-                                       true);
-        }
         // Insert the new frames at the beginning of the child list
         // and set their parent pointer
         const nsFrameList::Slice& newFrames =
           mFrames.InsertFrames(this, nullptr, *prevOverflowFrames);
         // If our prev in flow was under the first continuation of a first-line
         // frame then we need to reparent the style contexts to remove the
         // the special first-line styling. In the lazilySetParentPointer case
         // we reparent the style contexts when we set their parents in
@@ -389,24 +381,23 @@ nsInlineFrame::Reflow(nsPresContext*    
   }
 #endif
   if (!(GetStateBits() & NS_FRAME_FIRST_REFLOW)) {
     DrainFlags flags =
       lazilySetParentPointer ? eDontReparentFrames : DrainFlags(0);
     if (aReflowInput.mLineLayout->GetInFirstLine()) {
       flags = DrainFlags(flags | eInFirstLine);
     }
-    DrainSelfOverflowListInternal(flags, lineContainer);
+    DrainSelfOverflowListInternal(flags);
   }
 
-  // Set our own reflow state (additional state above and beyond
-  // aReflowInput)
+  // Set our own reflow state (additional state above and beyond aReflowInput).
   InlineReflowInput irs;
   irs.mPrevFrame = nullptr;
-  irs.mLineContainer = lineContainer;
+  irs.mLineContainer = aReflowInput.mLineLayout->LineContainerFrame();
   irs.mLineLayout = aReflowInput.mLineLayout;
   irs.mNextInFlow = (nsInlineFrame*) GetNextInFlow();
   irs.mSetParentPointer = lazilySetParentPointer;
 
   if (mFrames.IsEmpty()) {
     // Try to pull over one frame before starting so that we know
     // whether we have an anonymous block or not.
     bool complete;
@@ -441,29 +432,25 @@ nsInlineFrame::AttributeChanged(int32_t 
     f->HandleAttributeChangeInDescendant(mContent->AsElement(),
                                          aNameSpaceID, aAttribute);
   }
 
   return NS_OK;
 }
 
 bool
-nsInlineFrame::DrainSelfOverflowListInternal(DrainFlags aFlags,
-                                             nsIFrame* aLineContainer)
+nsInlineFrame::DrainSelfOverflowListInternal(DrainFlags aFlags)
 {
   AutoFrameListPtr overflowFrames(PresContext(), StealOverflowFrames());
   if (overflowFrames) {
     // The frames on our own overflowlist may have been pushed by a
     // previous lazilySetParentPointer Reflow so we need to ensure the
     // correct parent pointer.  This is sometimes skipped by Reflow.
     if (!(aFlags & eDontReparentFrames)) {
       nsIFrame* firstChild = overflowFrames->FirstChild();
-      if (aLineContainer && aLineContainer->GetPrevContinuation()) {
-        ReparentFloatsForInlineChild(aLineContainer, firstChild, true);
-      }
       const bool doReparentSC = (aFlags & eInFirstLine);
       RestyleManager* restyleManager = PresContext()->RestyleManager();
       for (nsIFrame* f = firstChild; f; f = f->GetNextSibling()) {
         f->SetParent(this);
         if (doReparentSC) {
           restyleManager->ReparentStyleContext(f);
           nsLayoutUtils::MarkDescendantsDirty(f);
         }
@@ -484,17 +471,17 @@ nsInlineFrame::DrainSelfOverflowList()
   // No need to look further than the nearest line container though.
   DrainFlags flags = DrainFlags(0);
   for (nsIFrame* p = GetParent(); p != lineContainer; p = p->GetParent()) {
     if (p->IsLineFrame()) {
       flags = DrainFlags(flags | eInFirstLine);
       break;
     }
   }
-  return DrainSelfOverflowListInternal(flags, lineContainer);
+  return DrainSelfOverflowListInternal(flags);
 }
 
 /* virtual */ bool
 nsInlineFrame::CanContinueTextRun() const
 {
   // We can continue a text run through an inline frame
   return true;
 }
@@ -553,33 +540,18 @@ nsInlineFrame::ReflowFrames(nsPresContex
                         startEdge + availableISize, &mBaseline);
 
   // First reflow our principal children.
   nsIFrame* frame = mFrames.FirstChild();
   bool done = false;
   while (frame) {
     // Check if we should lazily set the child frame's parent pointer.
     if (irs.mSetParentPointer) {
-      bool havePrevBlock =
-        irs.mLineContainer && irs.mLineContainer->GetPrevContinuation();
       nsIFrame* child = frame;
       do {
-        // If our block is the first in flow, then any floats under the pulled
-        // frame must already belong to our block.
-        if (havePrevBlock) {
-          // This has to happen before we update frame's parent; we need to
-          // know frame's ancestry under its old block.
-          // The blockChildren.ContainsFrame check performed by
-          // ReparentFloatsForInlineChild here may be slow, but we can't
-          // easily avoid it because we don't know where 'frame' originally
-          // came from. If we really really have to optimize this we could
-          // cache whether frame->GetParent() is under its containing blocks
-          // overflowList or not.
-          ReparentFloatsForInlineChild(irs.mLineContainer, child, false);
-        }
         child->SetParent(this);
         if (inFirstLine) {
           restyleManager->ReparentStyleContext(child);
           nsLayoutUtils::MarkDescendantsDirty(child);
         }
         // We also need to do the same for |frame|'s next-in-flows that are in
         // the sibling list. Otherwise, if we reflow |frame| and it's complete
         // we'll crash when trying to delete its next-in-flow.
@@ -1096,44 +1068,36 @@ nsFirstLineFrame::Reflow(nsPresContext* 
 {
   MarkInReflow();
   MOZ_ASSERT(aStatus.IsEmpty(), "Caller should pass a fresh reflow status!");
 
   if (nullptr == aReflowInput.mLineLayout) {
     return;  // XXX does this happen? why?
   }
 
-  nsIFrame* lineContainer = aReflowInput.mLineLayout->LineContainerFrame();
-
   // Check for an overflow list with our prev-in-flow
   nsFirstLineFrame* prevInFlow = (nsFirstLineFrame*)GetPrevInFlow();
   if (prevInFlow) {
     AutoFrameListPtr prevOverflowFrames(aPresContext,
                                         prevInFlow->StealOverflowFrames());
     if (prevOverflowFrames) {
-      // Assign all floats to our block if necessary
-      if (lineContainer && lineContainer->GetPrevContinuation()) {
-        ReparentFloatsForInlineChild(lineContainer,
-                                     prevOverflowFrames->FirstChild(),
-                                     true);
-      }
+      // Reparent the new frames and their style contexts.
       const nsFrameList::Slice& newFrames =
         mFrames.InsertFrames(this, nullptr, *prevOverflowFrames);
       ReparentChildListStyle(aPresContext, newFrames, this);
     }
   }
 
   // It's also possible that we have an overflow list for ourselves.
   DrainSelfOverflowList();
 
-  // Set our own reflow state (additional state above and beyond
-  // aReflowInput)
+  // Set our own reflow state (additional state above and beyond aReflowInput).
   InlineReflowInput irs;
   irs.mPrevFrame = nullptr;
-  irs.mLineContainer = lineContainer;
+  irs.mLineContainer = aReflowInput.mLineLayout->LineContainerFrame();
   irs.mLineLayout = aReflowInput.mLineLayout;
   irs.mNextInFlow = (nsInlineFrame*) GetNextInFlow();
 
   bool wasEmpty = mFrames.IsEmpty();
   if (wasEmpty) {
     // Try to pull over one frame before starting so that we know
     // whether we have an anonymous block or not.
     bool complete;

--- a/layout/generic/nsInlineFrame.h
+++ b/layout/generic/nsInlineFrame.h
@@ -176,21 +176,19 @@ private:
   // (which we only do for nsInlineFrame, not nsFirstLineFrame).
   enum DrainFlags {
     eDontReparentFrames = 1, // skip reparenting the overflow list frames
     eInFirstLine = 2, // the request is for an inline descendant of a nsFirstLineFrame
   };
   /**
    * Move any frames on our overflow list to the end of our principal list.
    * @param aFlags one or more of the above DrainFlags
-   * @param aLineContainer the nearest line container ancestor
    * @return true if there were any overflow frames
    */
-  bool DrainSelfOverflowListInternal(DrainFlags aFlags,
-                                     nsIFrame* aLineContainer);
+  bool DrainSelfOverflowListInternal(DrainFlags aFlags);
 protected:
   nscoord mBaseline;
 };
 
 //----------------------------------------------------------------------
 
 /**
  * Variation on inline-frame used to manage lines for line layout in

--- a/media/audioipc/audioipc/Cargo.toml
+++ b/media/audioipc/audioipc/Cargo.toml
@@ -6,16 +6,19 @@ authors = [
         "Dan Glastonbury <dan.glastonbury@gmail.com>"
         ]
 description = "Remote Cubeb IPC"
 
 [dependencies]
 cubeb-core = { path = "../../cubeb-rs/cubeb-core" }
 bincode = "0.8"
 bytes = "0.4"
-error-chain = "0.10.0"
 libc = "0.2"
 log = "^0.3.6"
 memmap = "0.5.2"
 mio = "0.6.7"
 mio-uds = "0.6.4"
 serde = "1.*.*"
 serde_derive = "1.*.*"
+
+[dependencies.error-chain]
+version = "0.10.0"
+default-features = false

--- a/media/audioipc/client/src/context.rs
+++ b/media/audioipc/client/src/context.rs
@@ -39,21 +39,26 @@ impl ClientContext {
         self.connection.lock().unwrap()
     }
 }
 
 impl Context for ClientContext {
     fn init(_context_name: Option<&CStr>) -> Result<*mut ffi::cubeb> {
         assert_not_in_callback();
         // TODO: encapsulate connect, etc inside audioipc.
+        // TODO: explicit setup of connection so we don't have to guess the
+        // path.  For now, we try our parent, ourself, and the default path.
         let ppid = unsafe { libc::getppid() };
-        let path = audioipc::get_uds_path(ppid as u64);
-        let stream = match UnixStream::connect(path) {
+        let pid = unsafe { libc::getpid() };
+        let stream = match UnixStream::connect(audioipc::get_uds_path(ppid as u64)) {
             Ok(stream) => stream,
-            _ => t!(UnixStream::connect(audioipc::get_uds_path(1)))
+            _ => match UnixStream::connect(audioipc::get_uds_path(pid as u64)) {
+                Ok(stream) => stream,
+                _ => t!(UnixStream::connect(audioipc::get_uds_path(1)))
+            }
         };
         let ctx = Box::new(ClientContext {
             _ops: &CLIENT_OPS as *const _,
             connection: Mutex::new(Connection::new(stream))
         });
         Ok(Box::into_raw(ctx) as *mut _)
     }
 

--- a/media/audioipc/server/Cargo.toml
+++ b/media/audioipc/server/Cargo.toml
@@ -4,16 +4,18 @@ version = "0.1.0"
 authors = ["Dan Glastonbury <dan.glastonbury@gmail.com>"]
 description = "Remote cubeb server"
 
 [dependencies]
 audioipc = { path = "../audioipc" }
 cubeb-core = { path = "../../cubeb-rs/cubeb-core" }
 cubeb = { path = "../../cubeb-rs/cubeb-api" }
 bytes = "0.4"
-error-chain = "0.10.0"
 lazycell = "^0.4"
 libc = "0.2"
 log = "^0.3.6"
 mio = "0.6.7"
 mio-uds = "0.6.4"
 slab = "0.3.0"
 
+[dependencies.error-chain]
+version = "0.10.0"
+default-features = false

--- a/modules/libjar/nsJARURI.cpp
+++ b/modules/libjar/nsJARURI.cpp
@@ -167,26 +167,26 @@ nsJARURI::GetInterfaces(uint32_t *count,
 NS_IMETHODIMP
 nsJARURI::GetScriptableHelper(nsIXPCScriptable **_retval)
 {
     *_retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsJARURI::GetContractID(char * *aContractID)
+nsJARURI::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsJARURI::GetClassDescription(char * *aClassDescription)
+nsJARURI::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = nullptr;
+    aClassDescription.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsJARURI::GetClassID(nsCID * *aClassID)
 {
     *aClassID = (nsCID*) moz_xmalloc(sizeof(nsCID));
     if (!*aClassID)

--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -2258,35 +2258,29 @@ private:
   bool mIsDefault;
 
   bool mFreeingObserverList;
   nsClassHashtable<PrefCallback, PrefCallback> mObservers;
 };
 
 class nsPrefLocalizedString final
   : public nsIPrefLocalizedString
-  , public nsISupportsString
 {
 public:
   nsPrefLocalizedString();
 
   NS_DECL_ISUPPORTS
+  NS_FORWARD_NSISUPPORTSPRIMITIVE(mUnicodeString->)
   NS_FORWARD_NSISUPPORTSSTRING(mUnicodeString->)
-  NS_FORWARD_NSISUPPORTSPRIMITIVE(mUnicodeString->)
 
   nsresult Init();
 
 private:
   virtual ~nsPrefLocalizedString();
 
-  NS_IMETHOD GetData(char16_t**) override;
-  NS_IMETHOD SetData(const char16_t* aData) override;
-  NS_IMETHOD SetDataWithLength(uint32_t aLength,
-                               const char16_t* aData) override;
-
   nsCOMPtr<nsISupportsString> mUnicodeString;
 };
 
 class nsRelativeFilePref : public nsIRelativeFilePref
 {
 public:
   NS_DECL_ISUPPORTS
   NS_DECL_NSIRELATIVEFILEPREF
@@ -2584,22 +2578,22 @@ nsPrefBranch::GetComplexValue(const char
     }
 
     // if we need to fetch the default value, do that instead, otherwise use the
     // value we pulled in at the top of this function
     if (bNeedDefault) {
       nsAutoString utf16String;
       rv = GetDefaultFromPropertiesFile(pref.get(), utf16String);
       if (NS_SUCCEEDED(rv)) {
-        theString->SetData(utf16String.get());
+        theString->SetData(utf16String);
       }
     } else {
       rv = GetCharPref(aPrefName, getter_Copies(utf8String));
       if (NS_SUCCEEDED(rv)) {
-        theString->SetData(NS_ConvertUTF8toUTF16(utf8String).get());
+        theString->SetData(NS_ConvertUTF8toUTF16(utf8String));
       }
     }
 
     if (NS_SUCCEEDED(rv)) {
       theString.forget(reinterpret_cast<nsIPrefLocalizedString**>(aRetVal));
     }
 
     return rv;
@@ -2848,17 +2842,18 @@ nsPrefBranch::SetComplexValue(const char
     nsAutoCString descriptorString;
     descriptorString.Append('[');
     descriptorString.Append(relativeToKey);
     descriptorString.Append(']');
     descriptorString.Append(relDescriptor);
     return SetCharPrefInternal(aPrefName, descriptorString.get());
   }
 
-  if (aType.Equals(NS_GET_IID(nsISupportsString))) {
+  if (aType.Equals(NS_GET_IID(nsISupportsString)) ||
+      aType.Equals(NS_GET_IID(nsIPrefLocalizedString))) {
     nsCOMPtr<nsISupportsString> theString = do_QueryInterface(aValue);
 
     if (theString) {
       nsString wideString;
 
       rv = theString->GetData(wideString);
       if (NS_SUCCEEDED(rv)) {
         // Check sanity of string length before any lengthy conversion
@@ -2868,35 +2863,16 @@ nsPrefBranch::SetComplexValue(const char
         }
         rv = SetCharPrefInternal(aPrefName,
                                  NS_ConvertUTF16toUTF8(wideString).get());
       }
     }
     return rv;
   }
 
-  if (aType.Equals(NS_GET_IID(nsIPrefLocalizedString))) {
-    nsCOMPtr<nsIPrefLocalizedString> theString = do_QueryInterface(aValue);
-
-    if (theString) {
-      nsString wideString;
-      rv = theString->GetData(getter_Copies(wideString));
-      if (NS_SUCCEEDED(rv)) {
-        // Check sanity of string length before any lengthy conversion
-        rv = CheckSanityOfStringLength(aPrefName, wideString);
-        if (NS_FAILED(rv)) {
-          return rv;
-        }
-        rv = SetCharPrefInternal(aPrefName,
-                                 NS_ConvertUTF16toUTF8(wideString).get());
-      }
-    }
-    return rv;
-  }
-
   NS_WARNING("nsPrefBranch::SetComplexValue - Unsupported interface type");
   return NS_NOINTERFACE;
 }
 
 NS_IMETHODIMP
 nsPrefBranch::ClearUserPref(const char* aPrefName)
 {
   ENSURE_MAIN_PROCESS("ClearUserPref", aPrefName);
@@ -3238,53 +3214,16 @@ nsresult
 nsPrefLocalizedString::Init()
 {
   nsresult rv;
   mUnicodeString = do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID, &rv);
 
   return rv;
 }
 
-NS_IMETHODIMP
-nsPrefLocalizedString::GetData(char16_t** aRetVal)
-{
-  nsAutoString data;
-
-  nsresult rv = GetData(data);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
-
-  *aRetVal = ToNewUnicode(data);
-  if (!*aRetVal) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
-
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-nsPrefLocalizedString::SetData(const char16_t* aData)
-{
-  if (!aData) {
-    return SetData(EmptyString());
-  }
-  return SetData(nsDependentString(aData));
-}
-
-NS_IMETHODIMP
-nsPrefLocalizedString::SetDataWithLength(uint32_t aLength,
-                                         const char16_t* aData)
-{
-  if (!aData) {
-    return SetData(EmptyString());
-  }
-  return SetData(Substring(aData, aLength));
-}
-
 //----------------------------------------------------------------------------
 // nsRelativeFilePref
 //----------------------------------------------------------------------------
 
 NS_IMPL_ISUPPORTS(nsRelativeFilePref, nsIRelativeFilePref)
 
 nsRelativeFilePref::nsRelativeFilePref() = default;
 
@@ -5025,17 +4964,17 @@ Preferences::GetLocalizedCString(const c
 Preferences::GetLocalizedString(const char* aPref, nsAString& aResult)
 {
   NS_ENSURE_TRUE(InitStaticMembers(), NS_ERROR_NOT_AVAILABLE);
   nsCOMPtr<nsIPrefLocalizedString> prefLocalString;
   nsresult rv = sRootBranch->GetComplexValue(
     aPref, NS_GET_IID(nsIPrefLocalizedString), getter_AddRefs(prefLocalString));
   if (NS_SUCCEEDED(rv)) {
     NS_ASSERTION(prefLocalString, "Succeeded but the result is NULL");
-    prefLocalString->GetData(getter_Copies(aResult));
+    prefLocalString->GetData(aResult);
   }
   return rv;
 }
 
 /* static */ nsresult
 Preferences::GetComplex(const char* aPref, const nsIID& aType, void** aResult)
 {
   NS_ENSURE_TRUE(InitStaticMembers(), NS_ERROR_NOT_AVAILABLE);
@@ -5505,17 +5444,17 @@ Preferences::GetDefaultLocalizedCString(
 Preferences::GetDefaultLocalizedString(const char* aPref, nsAString& aResult)
 {
   NS_ENSURE_TRUE(InitStaticMembers(), NS_ERROR_NOT_AVAILABLE);
   nsCOMPtr<nsIPrefLocalizedString> prefLocalString;
   nsresult rv = sDefaultRootBranch->GetComplexValue(
     aPref, NS_GET_IID(nsIPrefLocalizedString), getter_AddRefs(prefLocalString));
   if (NS_SUCCEEDED(rv)) {
     NS_ASSERTION(prefLocalString, "Succeeded but the result is NULL");
-    prefLocalString->GetData(getter_Copies(aResult));
+    prefLocalString->GetData(aResult);
   }
   return rv;
 }
 
 /* static */ nsresult
 Preferences::GetDefaultComplex(const char* aPref,
                                const nsIID& aType,
                                void** aResult)

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -635,16 +635,21 @@ pref("media.decoder.recycle.enabled", fa
 
 //Weather MFR should try to skip to next key frame or not.
 pref("media.decoder.skip-to-next-key-frame.enabled", true);
 
 // Log level for cubeb, the audio input/output system. Valid values are
 // "verbose", "normal" and "" (log disabled).
 pref("media.cubeb.logging_level", "");
 
+#ifdef NIGHTLY_BUILD
+// Cubeb sandbox (remoting) control
+pref("media.cubeb.sandbox", true);
+#endif
+
 // Set to true to force demux/decode warnings to be treated as errors.
 pref("media.playback.warnings-as-errors", false);
 
 // Weather we allow AMD switchable graphics
 pref("layers.amd-switchable-gfx.enabled", true);
 
 // Whether to use async panning and zooming
 pref("layers.async-pan-zoom.enabled", true);

--- a/modules/libpref/nsIPrefLocalizedString.idl
+++ b/modules/libpref/nsIPrefLocalizedString.idl
@@ -1,58 +1,28 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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 "nsISupports.idl"
+#include "nsISupportsPrimitives.idl"
 
 /**
  * The nsIPrefLocalizedString interface is simply a wrapper interface for
  * nsISupportsString so the preferences service can have a unique identifier
  * to distinguish between requests for normal wide strings (nsISupportsString)
  * and "localized" wide strings, which get their default values from properites
  * files.
  *
  * @see nsIPrefBranch
  * @see nsISupportsString
  */
-
 [scriptable, uuid(ae419e24-1dd1-11b2-b39a-d3e5e7073802)]
-interface nsIPrefLocalizedString : nsISupports
-{
-  /**
-   * Provides access to string data stored in this property.
-   *
-   * @throws Error An error occurred.
-   */
-  attribute wstring data;
-
-  /**
-   * Used to retrieve the contents of this object into a wide string.
-   *
-   * @return wstring The string containing the data stored within this object.
-   */
-  wstring toString();
-
-  /**
-   * Used to set the contents of this object.
-   *
-   * @param length The length of the string. This value should not include
-   *               space for the null terminator, nor should it account for the
-   *               size of a character. It should  only be the number of
-   *               characters for which there is space in the string.
-   * @param data   The string data to be stored.
-   *
-   * @note
-   * This makes a copy of the string argument passed in.
-   */
-  void setDataWithLength(in unsigned long length,
-                         [size_is(length)] in wstring data);
-};
+interface nsIPrefLocalizedString : nsISupportsString {};
 
 %{C++
 
 #define NS_PREFLOCALIZEDSTRING_CID                     \
   { /* {064d9cee-1dd2-11b2-83e3-d25ab0193c26} */       \
     0x064d9cee,                                        \
     0x1dd2,                                            \
     0x11b2,                                            \

--- a/netwerk/base/RustURL.cpp
+++ b/netwerk/base/RustURL.cpp
@@ -676,26 +676,26 @@ RustURL::GetInterfaces(uint32_t *count, 
 NS_IMETHODIMP
 RustURL::GetScriptableHelper(nsIXPCScriptable * *_retval)
 {
   *_retval = nullptr;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-RustURL::GetContractID(char * *aContractID)
+RustURL::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-RustURL::GetClassDescription(char * *aClassDescription)
+RustURL::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 RustURL::GetClassID(nsCID **aClassID)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }

--- a/netwerk/base/nsSimpleURI.cpp
+++ b/netwerk/base/nsSimpleURI.cpp
@@ -739,28 +739,28 @@ nsSimpleURI::GetInterfaces(uint32_t *cou
 NS_IMETHODIMP
 nsSimpleURI::GetScriptableHelper(nsIXPCScriptable **_retval)
 {
     *_retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSimpleURI::GetContractID(char * *aContractID)
+nsSimpleURI::GetContractID(nsACString& aContractID)
 {
     // Make sure to modify any subclasses as needed if this ever
     // changes.
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSimpleURI::GetClassDescription(char * *aClassDescription)
+nsSimpleURI::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = nullptr;
+    aClassDescription.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsSimpleURI::GetClassID(nsCID * *aClassID)
 {
     // Make sure to modify any subclasses as needed if this ever
     // changes to not call the virtual GetClassIDNoAlloc.

--- a/netwerk/base/nsSocketTransport2.cpp
+++ b/netwerk/base/nsSocketTransport2.cpp
@@ -2966,26 +2966,26 @@ nsSocketTransport::GetInterfaces(uint32_
 NS_IMETHODIMP
 nsSocketTransport::GetScriptableHelper(nsIXPCScriptable **_retval)
 {
     *_retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSocketTransport::GetContractID(char * *aContractID)
+nsSocketTransport::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSocketTransport::GetClassDescription(char * *aClassDescription)
+nsSocketTransport::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = nullptr;
+    aClassDescription.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsSocketTransport::GetClassID(nsCID * *aClassID)
 {
     *aClassID = nullptr;
     return NS_OK;

--- a/netwerk/base/nsStandardURL.cpp
+++ b/netwerk/base/nsStandardURL.cpp
@@ -3833,26 +3833,26 @@ nsStandardURL::GetInterfaces(uint32_t *c
 NS_IMETHODIMP
 nsStandardURL::GetScriptableHelper(nsIXPCScriptable **_retval)
 {
     *_retval = nullptr;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsStandardURL::GetContractID(char * *aContractID)
+nsStandardURL::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsStandardURL::GetClassDescription(char * *aClassDescription)
+nsStandardURL::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = nullptr;
+    aClassDescription.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
 nsStandardURL::GetClassID(nsCID * *aClassID)
 {
     *aClassID = (nsCID*) moz_xmalloc(sizeof(nsCID));
     if (!*aClassID)

--- a/security/manager/ssl/TransportSecurityInfo.cpp
+++ b/security/manager/ssl/TransportSecurityInfo.cpp
@@ -427,26 +427,26 @@ TransportSecurityInfo::GetInterfaces(uin
 NS_IMETHODIMP
 TransportSecurityInfo::GetScriptableHelper(nsIXPCScriptable **_retval)
 {
   *_retval = nullptr;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-TransportSecurityInfo::GetContractID(char * *aContractID)
+TransportSecurityInfo::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-TransportSecurityInfo::GetClassDescription(char * *aClassDescription)
+TransportSecurityInfo::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 TransportSecurityInfo::GetClassID(nsCID * *aClassID)
 {
   *aClassID = (nsCID*) moz_xmalloc(sizeof(nsCID));
   if (!*aClassID)

--- a/security/manager/ssl/nsNSSCertificate.cpp
+++ b/security/manager/ssl/nsNSSCertificate.cpp
@@ -1533,26 +1533,26 @@ nsNSSCertificate::GetInterfaces(uint32_t
 NS_IMETHODIMP
 nsNSSCertificate::GetScriptableHelper(nsIXPCScriptable** _retval)
 {
   *_retval = nullptr;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsNSSCertificate::GetContractID(char** aContractID)
+nsNSSCertificate::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsNSSCertificate::GetClassDescription(char** aClassDescription)
+nsNSSCertificate::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsNSSCertificate::GetClassID(nsCID** aClassID)
 {
   *aClassID = (nsCID*) moz_xmalloc(sizeof(nsCID));
   if (!*aClassID)

--- a/security/manager/ssl/nsSSLStatus.cpp
+++ b/security/manager/ssl/nsSSLStatus.cpp
@@ -289,26 +289,26 @@ nsSSLStatus::GetInterfaces(uint32_t* aCo
 NS_IMETHODIMP
 nsSSLStatus::GetScriptableHelper(nsIXPCScriptable** aHelper)
 {
   *aHelper = nullptr;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSSLStatus::GetContractID(char** aContractID)
+nsSSLStatus::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSSLStatus::GetClassDescription(char** aClassDescription)
+nsSSLStatus::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsSSLStatus::GetClassID(nsCID** aClassID)
 {
   *aClassID = (nsCID*) moz_xmalloc(sizeof(nsCID));
   if (!*aClassID) {

--- a/storage/mozStorageAsyncStatement.cpp
+++ b/storage/mozStorageAsyncStatement.cpp
@@ -58,26 +58,26 @@ public:
   GetScriptableHelper(nsIXPCScriptable **_helper) override
   {
     static AsyncStatementJSHelper sJSHelper;
     *_helper = &sJSHelper;
     return NS_OK;
   }
 
   NS_IMETHOD
-  GetContractID(char **_contractID) override
+  GetContractID(nsACString& aContractID) override
   {
-    *_contractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
   }
 
   NS_IMETHOD
-  GetClassDescription(char **_desc) override
+  GetClassDescription(nsACString& aDesc) override
   {
-    *_desc = nullptr;
+    aDesc.SetIsVoid(true);
     return NS_OK;
   }
 
   NS_IMETHOD
   GetClassID(nsCID **_id) override
   {
     *_id = nullptr;
     return NS_OK;

--- a/storage/mozStorageStatement.cpp
+++ b/storage/mozStorageStatement.cpp
@@ -61,26 +61,26 @@ public:
   GetScriptableHelper(nsIXPCScriptable **_helper) override
   {
     static StatementJSHelper sJSHelper;
     *_helper = &sJSHelper;
     return NS_OK;
   }
 
   NS_IMETHOD
-  GetContractID(char **_contractID) override
+  GetContractID(nsACString& aContractID) override
   {
-    *_contractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
   }
 
   NS_IMETHOD
-  GetClassDescription(char **_desc) override
+  GetClassDescription(nsACString& aDesc) override
   {
-    *_desc = nullptr;
+    aDesc.SetIsVoid(true);
     return NS_OK;
   }
 
   NS_IMETHOD
   GetClassID(nsCID **_id) override
   {
     *_id = nullptr;
     return NS_OK;

--- a/testing/web-platform/meta/dom/interfaces.html.ini
+++ b/testing/web-platform/meta/dom/interfaces.html.ini
@@ -1,10 +1,11 @@
 [interfaces.html]
   type: testharness
+  prefs: [dom.webcomponents.enabled:true]
   [Document interface: attribute origin]
     expected: FAIL
     bug: 931884
 
   [Document interface: xmlDoc must inherit property "origin" with the proper type (3)]
     expected: FAIL
     bug: 931884
 
@@ -19,34 +20,28 @@
     expected: FAIL
 
   [Element interface: attribute slot]
     expected: FAIL
 
   [Element interface: operation attachShadow(ShadowRootInit)]
     expected: FAIL
 
-  [Element interface: attribute assignedSlot]
-    expected: FAIL
-
   [Element interface: element must inherit property "slot" with the proper type (7)]
     expected: FAIL
 
   [Element interface: element must inherit property "attachShadow" with the proper type (24)]
     expected: FAIL
 
   [Element interface: calling attachShadow(ShadowRootInit) on element with too few arguments must throw TypeError]
     expected: FAIL
 
   [Element interface: element must inherit property "assignedSlot" with the proper type (48)]
     expected: FAIL
 
-  [Text interface: attribute assignedSlot]
-    expected: FAIL
-
   [Text interface: document.createTextNode("abc") must inherit property "assignedSlot" with the proper type (2)]
     expected: FAIL
 
   [EventTarget must be primary interface of new EventTarget()]
     expected: FAIL
 
   [Stringification of new EventTarget()]
     expected: FAIL
@@ -97,14 +92,8 @@
     expected: FAIL
 
   [Element interface: element must inherit property "slot" with the proper type]
     expected: FAIL
 
   [Element interface: element must inherit property "attachShadow(ShadowRootInit)" with the proper type]
     expected: FAIL
 
-  [Element interface: element must inherit property "assignedSlot" with the proper type]
-    expected: FAIL
-
-  [Text interface: document.createTextNode("abc") must inherit property "assignedSlot" with the proper type]
-    expected: FAIL
-

--- a/testing/web-platform/meta/payment-request/interfaces.https.html.ini
+++ b/testing/web-platform/meta/payment-request/interfaces.https.html.ini
@@ -1,10 +1,11 @@
 [interfaces.https.html]
   type: testharness
+  prefs: [dom.webcomponents.enabled:true]
   [PaymentRequest interface: existence and properties of interface object]
     expected: FAIL
 
   [PaymentRequest interface object length]
     expected: FAIL
 
   [PaymentRequest interface object name]
     expected: FAIL
@@ -271,22 +272,16 @@
     expected: FAIL
 
   [Element interface: attribute slot]
     expected: FAIL
 
   [Element interface: operation attachShadow(ShadowRootInit)]
     expected: FAIL
 
-  [Element interface: attribute assignedSlot]
-    expected: FAIL
-
-  [Text interface: attribute assignedSlot]
-    expected: FAIL
-
   [PaymentRequest must be primary interface of new PaymentRequest([{supportedMethods: 'foo'}\], {total: {label: 'bar', amount: {currency: 'USD', value: '0'}} })]
     expected: FAIL
 
   [Stringification of new PaymentRequest([{supportedMethods: 'foo'}\], {total: {label: 'bar', amount: {currency: 'USD', value: '0'}} })]
     expected: FAIL
 
   [PaymentRequest interface: new PaymentRequest([{supportedMethods: 'foo'}\], {total: {label: 'bar', amount: {currency: 'USD', value: '0'}} }) must inherit property "show()" with the proper type]
     expected: FAIL

--- a/testing/web-platform/meta/shadow-dom/Slotable-interface.html.ini
+++ b/testing/web-platform/meta/shadow-dom/Slotable-interface.html.ini
@@ -1,13 +1,11 @@
 [Slotable-interface.html]
   type: testharness
-  [assignedSlot attribute must be defined on Element and Text interfaces]
-    expected: FAIL
-
+  prefs: [dom.webcomponents.enabled:true]
   [assignedSlot must return null when the node does not have an assigned node]
     expected: FAIL
 
   [assignedSlot must return the assigned slot]
     expected: FAIL
 
   [assignedSlot must return null when the assigned slot element is inside a closed shadow tree]
     expected: FAIL

--- a/toolkit/content/browser-content.js
+++ b/toolkit/content/browser-content.js
@@ -1785,16 +1785,24 @@ let DateTimePickerListener = {
   handleEvent(aEvent) {
     switch (aEvent.type) {
       case "MozOpenDateTimePicker": {
         // Time picker is disabled when preffed off
         if (!(aEvent.originalTarget instanceof content.HTMLInputElement) ||
             (aEvent.originalTarget.type == "time" && !this.getTimePickerPref())) {
           return;
         }
+
+        if (this._inputElement) {
+          // This happens when we're trying to open a picker when another picker
+          // is still open. We ignore this request to let the first picker
+          // close gracefully.
+          return;
+        }
+
         this._inputElement = aEvent.originalTarget;
         this._inputElement.setDateTimePickerState(true);
         this.addListeners();
 
         let value = this._inputElement.getDateTimeInputBoxValue();
         sendAsyncMessage("FormDateTime:OpenPicker", {
           rect: this.getBoundingContentRect(this._inputElement),
           dir: this.getComputedDirection(this._inputElement),

--- a/toolkit/library/gtest/rust/Cargo.lock
+++ b/toolkit/library/gtest/rust/Cargo.lock
@@ -104,39 +104,16 @@ dependencies = [
  "libc 0.2.24 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "mio 0.6.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "mio-uds 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "slab 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
-name = "backtrace"
-version = "0.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "backtrace-sys 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "cfg-if 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "dbghelp-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.24 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc-demangle 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
-name = "backtrace-sys"
-version = "0.1.10"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.24 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
 name = "binary-space-partition"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "bincode"
 version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -404,25 +381,16 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "darling_core 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
-name = "dbghelp-sys"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
 name = "dtoa"
 version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "dtoa-short"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -483,19 +451,16 @@ dependencies = [
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "error-chain"
 version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "backtrace 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
-]
 
 [[package]]
 name = "euclid"
 version = "0.15.2"
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@@ -551,21 +516,16 @@ dependencies = [
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 dependencies = [
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 [[package]]
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 "checksum bitflags 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1370e9fc2a6ae53aea8b7a5110edbd08836ed87c88736dfabccade1c2b44bff4"
 "checksum bitflags 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)" = "4efd02e230a02e18f92fc2735f44597385ed02ad8f831e7c1c1156ee5e1ab3a5"
 "checksum bitflags 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f5cde24d1b2e2216a726368b2363a273739c91f4e3eb4e0dd12d672d396ad989"
@@ -1708,33 +1661,31 @@ dependencies = [
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-"checksum gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)" = "120d07f202dcc3f72859422563522b66fe6463a4c513df062874daad05f85f0a"
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 "checksum gleam 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)" = "bf887141f0c2a83eae026cbf3fba74f0a5cb0f01d20e5cdfcd8c4ad39295be1e"
 "checksum glob 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "8be18de09a56b60ed0edf84bc9df007e30040691af7acd1c41874faac5895bfb"
 "checksum heapsize 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "4c7593b1522161003928c959c20a2ca421c68e940d63d75573316a009e48a6d4"
 "checksum ident_case 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3c9826188e666f2ed92071d2dadef6edc430b11b158b5b2b3f4babbcc891eaaa"
 "checksum idna 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "014b298351066f1512874135335d62a789ffe78a9974f94b43ed5621951eaf7d"
 "checksum iovec 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "29d062ee61fccdf25be172e70f34c9f6efc597e1fb8f6526e8437b2046ab26be"
@@ -1781,17 +1732,16 @@ dependencies = [
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 "checksum rayon 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)" = "b614fe08b6665cb9a231d07ac1364b0ef3cb3698f1239ee0c4c3a88a524f54c8"
 "checksum rayon-core 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e2c21a92a5dca958fb030787c1158446c6deb7f976399b72fa8074603f169e2a"
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-"checksum rustc-demangle 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "3058a43ada2c2d0b92b3ae38007a2d0fa5e9db971be260e0171408a4ff471c95"
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--- a/toolkit/library/rust/Cargo.lock
+++ b/toolkit/library/rust/Cargo.lock
@@ -103,39 +103,16 @@ dependencies = [
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  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "mio 0.6.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "mio-uds 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "slab 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
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 [[package]]
-name = "backtrace"
-version = "0.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "backtrace-sys 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "cfg-if 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "dbghelp-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.24 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc-demangle 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
-name = "backtrace-sys"
-version = "0.1.10"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.24 (registry+https://github.com/rust-lang/crates.io-index)",
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-
-[[package]]
 name = "binary-space-partition"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "bincode"
 version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -403,25 +380,16 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "darling_core 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
-name = "dbghelp-sys"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
 name = "dtoa"
 version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "dtoa-short"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -482,19 +450,16 @@ dependencies = [
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  "regex 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
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 source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
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-]
 
 [[package]]
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  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -550,21 +515,16 @@ dependencies = [
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 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
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-source = "registry+https://github.com/rust-lang/crates.io-index"
-
-[[package]]
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 dependencies = [
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  "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1156,21 +1116,16 @@ version = "0.0.1"
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 [[package]]
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-version = "0.1.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
-[[package]]
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 version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "same-file"
 version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1691,18 +1646,16 @@ dependencies = [
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 "checksum atomic_refcell 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fb2dcb6e6d35f20276943cc04bb98e538b348d525a04ac79c10021561d202f21"
 "checksum atty 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "d912da0db7fa85514874458ca3651fe2cddace8d0b0505571dbdcd41ab490159"
-"checksum backtrace 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "72f9b4182546f4b04ebc4ab7f84948953a118bd6021a1b6a6c909e3e94f6be76"
-"checksum backtrace-sys 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "d192fd129132fbc97497c1f2ec2c2c5174e376b95f535199ef4fe0a293d33842"
 "checksum binary-space-partition 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "88ceb0d16c4fd0e42876e298d7d3ce3780dd9ebdcbe4199816a32c77e08597ff"
 "checksum bincode 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e103c8b299b28a9c6990458b7013dc4a8356a9b854c51b9883241f5866fac36e"
 "checksum bincode 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)" = "9d3fb369af639822830328794eba2501b3479652fcd021b2aeb1ed4984202afd"
 "checksum bindgen 0.29.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ba610cba0c1727ed837316540068b51349b8268c073906067b7c3948598929bd"
 "checksum bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "aad18937a628ec6abcd26d1489012cc0e18c21798210f491af69ded9b881106d"
 "checksum bitflags 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1370e9fc2a6ae53aea8b7a5110edbd08836ed87c88736dfabccade1c2b44bff4"
 "checksum bitflags 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)" = "4efd02e230a02e18f92fc2735f44597385ed02ad8f831e7c1c1156ee5e1ab3a5"
 "checksum bitflags 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f5cde24d1b2e2216a726368b2363a273739c91f4e3eb4e0dd12d672d396ad989"
@@ -1720,33 +1673,31 @@ dependencies = [
 "checksum core-foundation-sys 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "bc9fb3d6cb663e6fd7cf1c63f9b144ee2b1e4a78595a0451dd34bff85b9a3387"
 "checksum core-graphics 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)" = "2fd47addfc77b7e574d24e5434f95bb64a863769dfd4f1d451ca4ff5530ba01a"
 "checksum core-text 7.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2a23bef779fab70e5e6af23e36eed03a48e1c1687dea8929505d405ea48d1f5e"
 "checksum cssparser 0.22.0 (registry+https://github.com/rust-lang/crates.io-index)" = "44313341610282488e1156ad1fedebca51c54766c87a041d0287b10499c04ba1"
 "checksum cssparser-macros 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "079adec4af52bb5275eadd004292028c79eb3c5f5b4ee8086a36d4197032f6df"
 "checksum darling 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9861a8495606435477df581bc858ccf15a3469747edf175b94a4704fd9aaedac"
 "checksum darling_core 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1486a8b00b45062c997f767738178b43219133dd0c8c826cb811e60563810821"
 "checksum darling_macro 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8a86ec160aa0c3dd492dd4a14ec8104ad8f1a9400a820624db857998cc1f80f9"
-"checksum dbghelp-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "97590ba53bcb8ac28279161ca943a924d1fd4a8fb3fa63302591647c4fc5b850"
 "checksum dtoa 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "09c3753c3db574d215cba4ea76018483895d7bff25a31b49ba45db21c48e50ab"
 "checksum dtoa-short 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "068d4026697c1a18f0b0bb8cfcad1b0c151b90d8edb9bf4c235ad68128920d1d"
 "checksum dwrote 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "36e3b27cd0b8a68e00f07e8d8e1e4f4d8a6b8b873290a734f63bd56d792d23e1"
 "checksum either 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "18785c1ba806c258137c937e44ada9ee7e69a37e3c72077542cd2f069d78562a"
 "checksum encoding_c 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "93ec52324ca72f423237a413ca0e1c60654c8b3d0934fcd5fd888508dfcc4ba7"
 "checksum encoding_rs 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f5215aabf22b83153be3ee44dfe3f940214541b2ce13d419c55e7a115c8c51a9"
 "checksum env_logger 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)" = "3ddf21e73e016298f5cb37d6ef8e8da8e39f91f9ec8b0df44b7deb16a9f8cd5b"
 "checksum error-chain 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d9435d864e017c3c6afeac1654189b06cdb491cf2ff73dbf0d73b0f292f42ff8"
 "checksum euclid 0.15.2 (registry+https://github.com/rust-lang/crates.io-index)" = "50c9e4c3b53de731815135191f0b77969bea953211b8bbd3cc3083a7b10e190e"
 "checksum fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "6cc484842f1e2884faf56f529f960cc12ad8c71ce96cc7abba0a067c98fee344"
 "checksum freetype 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "398b8a11884898184d55aca9806f002b3cf68f0e860e0cbb4586f834ee39b0e7"
 "checksum fs2 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "9ab76cfd2aaa59b7bf6688ad9ba15bbae64bff97f04ea02144cfd3443e5c2866"
 "checksum futures 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "55f0008e13fc853f79ea8fc86e931486860d4c4c156cdffb59fa5f7fa833660a"
 "checksum fxhash 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c31b6d751ae2c7f11320402d34e41349dd1016f8d5d45e48c4312bc8625af50c"
 "checksum gamma-lut 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "dd65074503368cef99b98844012adfed8d7f99ff3e1e6d05e9055232f2d59dc9"
-"checksum gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)" = "120d07f202dcc3f72859422563522b66fe6463a4c513df062874daad05f85f0a"
 "checksum gdi32-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0912515a8ff24ba900422ecda800b52f4016a56251922d397c576bf92c690518"
 "checksum gl_generator 0.5.3 (registry+https://github.com/rust-lang/crates.io-index)" = "0940975a4ca12b088d32b5d5134826c47d2e73de4b0b459b05244c01503eccbb"
 "checksum gleam 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)" = "bf887141f0c2a83eae026cbf3fba74f0a5cb0f01d20e5cdfcd8c4ad39295be1e"
 "checksum glob 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "8be18de09a56b60ed0edf84bc9df007e30040691af7acd1c41874faac5895bfb"
 "checksum heapsize 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "4c7593b1522161003928c959c20a2ca421c68e940d63d75573316a009e48a6d4"
 "checksum ident_case 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3c9826188e666f2ed92071d2dadef6edc430b11b158b5b2b3f4babbcc891eaaa"
 "checksum idna 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "014b298351066f1512874135335d62a789ffe78a9974f94b43ed5621951eaf7d"
 "checksum iovec 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "29d062ee61fccdf25be172e70f34c9f6efc597e1fb8f6526e8437b2046ab26be"
@@ -1793,17 +1744,16 @@ dependencies = [
 "checksum quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e920b65c65f10b2ae65c831a81a073a89edd28c7cce89475bff467ab4167a"
 "checksum rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)" = "022e0636ec2519ddae48154b028864bdce4eaf7d35226ab8e65c611be97b189d"
 "checksum rayon 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)" = "b614fe08b6665cb9a231d07ac1364b0ef3cb3698f1239ee0c4c3a88a524f54c8"
 "checksum rayon-core 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e2c21a92a5dca958fb030787c1158446c6deb7f976399b72fa8074603f169e2a"
 "checksum redox_syscall 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)" = "8dd35cc9a8bdec562c757e3d43c1526b5c6d2653e23e2315065bc25556550753"
 "checksum regex 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1731164734096285ec2a5ec7fea5248ae2f5485b3feeb0115af4fda2183b2d1b"
 "checksum regex-syntax 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ad890a5eef7953f55427c50575c680c42841653abd2b028b68cd223d157f62db"
 "checksum runloop 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5d79b4b604167921892e84afbbaad9d5ad74e091bf6c511d9dbfb0593f09fabd"
-"checksum rustc-demangle 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "3058a43ada2c2d0b92b3ae38007a2d0fa5e9db971be260e0171408a4ff471c95"
 "checksum rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)" = "dcf128d1287d2ea9d80910b5f1120d0b8eede3fbf1abe91c40d39ea7d51e6fda"
 "checksum same-file 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "d931a44fdaa43b8637009e7632a02adc4f2b2e0733c08caa4cf00e8da4a117a7"
 "checksum scopeguard 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "c79eb2c3ac4bc2507cda80e7f3ac5b88bd8eae4c0914d5663e6a8933994be918"
 "checksum semver 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a3186ec9e65071a2095434b1f5bb24838d4e8e130f584c790f6033c79943537"
 "checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 "checksum serde 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)" = "c2f530d36fb84ec48fb7146936881f026cdbf4892028835fd9398475f82c1bb4"
 "checksum serde_derive 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)" = "10552fad5500771f3902d0c5ba187c5881942b811b7ba0d8fbbfbf84d80806d3"
 "checksum serde_derive_internals 0.15.1 (registry+https://github.com/rust-lang/crates.io-index)" = "37aee4e0da52d801acfbc0cc219eb1eda7142112339726e427926a6f6ee65d3a"

--- a/toolkit/library/rust/gkrust-features.mozbuild
+++ b/toolkit/library/rust/gkrust-features.mozbuild
@@ -18,12 +18,14 @@ if CONFIG['MOZ_BUILD_WEBRENDER']:
     gkrust_features += ['quantum_render']
 
 if CONFIG['MOZ_PULSEAUDIO']:
     gkrust_features += ['cubeb_pulse_rust']
 
 if CONFIG['MOZ_RUST_SIMD']:
     gkrust_features += ['simd-accel']
 
-if CONFIG['MOZ_CUBEB_REMOTING']:
+# This feature is only supported on Linux and this check needs to
+# match MOZ_CUBEB_REMOTING in CubebUtils.cpp.
+if CONFIG['OS_ARCH'] == 'Linux' and CONFIG['OS_TARGET'] != 'Android':
     gkrust_features += ['cubeb-remoting']
 
 gkrust_features += ['no-static-ideograph-encoder-tables']

--- a/toolkit/modules/DateTimePickerHelper.jsm
+++ b/toolkit/modules/DateTimePickerHelper.jsm
@@ -58,16 +58,17 @@ this.DateTimePickerHelper = {
         this.showPicker(aMessage.target, aMessage.data);
         break;
       }
       case "FormDateTime:ClosePicker": {
         if (!this.picker) {
           return;
         }
         this.picker.closePicker();
+        this.close();
         break;
       }
       case "FormDateTime:UpdatePicker": {
         if (!this.picker) {
           return;
         }
         this.picker.setPopupValue(aMessage.data);
         break;

--- a/toolkit/moz.configure
+++ b/toolkit/moz.configure
@@ -1139,30 +1139,16 @@ def geckodriver(enable, automation, comp
         linux32 = target.kernel == 'Linux' and target.cpu == 'x86'
         broken_platforms = cross_compile or linux32 or hazard
 
         if automation and compile_env and not broken_platforms:
             return True
 
 set_config('ENABLE_GECKODRIVER', geckodriver)
 
-# Cubeb Audio Remoting
-# ==============================================================
-
-option('--enable-cubeb-remoting', env='MOZ_CUBEB_REMOTING',
-       help='Enable cubeb audio remoting')
-
-@depends('--enable-cubeb-remoting')
-def cubeb_remoting(value):
-    if value:
-        return True
-
-set_config('MOZ_CUBEB_REMOTING', cubeb_remoting)
-set_define('MOZ_CUBEB_REMOTING', cubeb_remoting)
-
 # WebRTC
 # ========================================================
 @depends(target)
 def webrtc_default(target):
     # Turn off webrtc for OS's we don't handle yet, but allow
     # --enable-webrtc to override.
     os_match = False
     for os_fragment in ('linux', 'mingw', 'android', 'linuxandroid',

--- a/widget/cocoa/nsCocoaWindow.h
+++ b/widget/cocoa/nsCocoaWindow.h
@@ -245,16 +245,17 @@ public:
     virtual void            ConstrainPosition(bool aAllowSlop,
                                               int32_t *aX, int32_t *aY) override;
     virtual void            SetSizeConstraints(const SizeConstraints& aConstraints) override;
     virtual void            Move(double aX, double aY) override;
     virtual void            SetSizeMode(nsSizeMode aMode) override;
     virtual void            SuppressAnimation(bool aSuppress) override;
     virtual void            HideWindowChrome(bool aShouldHide) override;
 
+    void WillEnterFullScreen(bool aFullScreen);
     void EnteredFullScreen(bool aFullScreen, bool aNativeMode = true);
     virtual bool PrepareForFullscreenTransition(nsISupports** aData) override;
     virtual void PerformFullscreenTransition(FullscreenTransitionStage aStage,
                                              uint16_t aDuration,
                                              nsISupports* aData,
                                              nsIRunnable* aCallback) override;
     virtual nsresult MakeFullScreen(
       bool aFullScreen, nsIScreen* aTargetScreen = nullptr) override final;

--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -1486,16 +1486,23 @@ nsCocoaWindow::PerformFullscreenTransiti
   };
   mFullscreenTransitionAnimation =
     [[NSViewAnimation alloc] initWithViewAnimations:@[dict]];
   [mFullscreenTransitionAnimation setDelegate:delegate];
   [mFullscreenTransitionAnimation setDuration:aDuration / 1000.0];
   [mFullscreenTransitionAnimation startAnimation];
 }
 
+void nsCocoaWindow::WillEnterFullScreen(bool aFullScreen)
+{
+  if (mWidgetListener) {
+    mWidgetListener->FullscreenWillChange(aFullScreen);
+  }
+}
+
 void nsCocoaWindow::EnteredFullScreen(bool aFullScreen, bool aNativeMode)
 {
   mInFullScreenTransition = false;
   bool wasInFullscreen = mInFullScreenMode;
   mInFullScreenMode = aFullScreen;
   if (aNativeMode || mInNativeFullScreenMode) {
     mInNativeFullScreenMode = aFullScreen;
   }
@@ -2637,16 +2644,25 @@ nsCocoaWindow::GetEditCommands(NativeKey
     if (GetBackingScaleFactor(window) != mGeckoWindow->BackingScaleFactor()) {
       mGeckoWindow->BackingScaleFactorChanged();
     }
   }
 
   mGeckoWindow->ReportMoveEvent();
 }
 
+- (void)windowWillEnterFullScreen:(NSNotification *)notification
+{
+  if (!mGeckoWindow) {
+    return;
+  }
+
+  mGeckoWindow->WillEnterFullScreen(true);
+}
+
 // Lion's full screen mode will bypass our internal fullscreen tracking, so
 // we need to catch it when we transition and call our own methods, which in
 // turn will fire "fullscreen" events.
 - (void)windowDidEnterFullScreen:(NSNotification *)notification
 {
   if (!mGeckoWindow) {
     return;
   }
@@ -2672,16 +2688,25 @@ nsCocoaWindow::GetEditCommands(NativeKey
   if ([titlebarView respondsToSelector:@selector(setTransparent:)]) {
     [titlebarView setTransparent:NO];
   }
   if ([titlebarContainerView respondsToSelector:@selector(setTransparent:)]) {
     [titlebarContainerView setTransparent:NO];
   }
 }
 
+- (void)windowWillExitFullScreen:(NSNotification *)notification
+{
+  if (!mGeckoWindow) {
+    return;
+  }
+
+  mGeckoWindow->WillEnterFullScreen(false);
+}
+
 - (void)windowDidExitFullScreen:(NSNotification *)notification
 {
   if (!mGeckoWindow) {
     return;
   }
 
   mGeckoWindow->EnteredFullScreen(false);
 }

--- a/widget/nsIWidgetListener.cpp
+++ b/widget/nsIWidgetListener.cpp
@@ -55,16 +55,21 @@ nsIWidgetListener::SizeModeChanged(nsSiz
 }
 
 void
 nsIWidgetListener::UIResolutionChanged()
 {
 }
 
 void
+nsIWidgetListener::FullscreenWillChange(bool aInFullscreen)
+{
+}
+
+void
 nsIWidgetListener::FullscreenChanged(bool aInFullscreen)
 {
 }
 
 bool
 nsIWidgetListener::ZLevelChanged(bool aImmediate,
                                  nsWindowZ* aPlacement,
                                  nsIWidget* aRequestBelow,

--- a/widget/nsIWidgetListener.h
+++ b/widget/nsIWidgetListener.h
@@ -92,16 +92,21 @@ public:
    * window to place below. On return, aActualBelow will be set to the
    * window actually behind. This generally only applies to Windows.
    */
   virtual bool ZLevelChanged(bool aImmediate, nsWindowZ* aPlacement,
                              nsIWidget* aRequestBelow,
                              nsIWidget** aActualBelow);
 
   /**
+   * Called when the window will enter or leave the fullscreen state.
+   */
+  virtual void FullscreenWillChange(bool aInFullscreen);
+
+  /**
    * Called when the window entered or left the fullscreen state.
    */
   virtual void FullscreenChanged(bool aInFullscreen);
 
   /**
    * Called when the occlusion state is changed.
    */
   virtual void OcclusionStateChanged(bool aIsFullyOccluded);

--- a/xpcom/base/nsClassInfoImpl.cpp
+++ b/xpcom/base/nsClassInfoImpl.cpp
@@ -31,27 +31,27 @@ GenericClassInfo::GetScriptableHelper(ns
 {
   if (mData->getscriptablehelper) {
     return mData->getscriptablehelper(aHelper);
   }
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
-GenericClassInfo::GetContractID(char** aContractID)
+GenericClassInfo::GetContractID(nsACString& aContractID)
 {
   NS_ERROR("GetContractID not implemented");
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
-GenericClassInfo::GetClassDescription(char** aDescription)
+GenericClassInfo::GetClassDescription(nsACString& aDescription)
 {
-  *aDescription = nullptr;
+  aDescription.SetIsVoid(true);
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
 GenericClassInfo::GetClassID(nsCID** aClassID)
 {
   NS_ERROR("GetClassID not implemented");
   *aClassID = nullptr;

--- a/xpcom/base/nsISupportsImpl.h
+++ b/xpcom/base/nsISupportsImpl.h
@@ -1201,26 +1201,26 @@ NS_IMETHODIMP                           
 NS_IMETHODIMP                                                                 \
 _class::GetScriptableHelper(nsIXPCScriptable** _retval)                       \
 {                                                                             \
   *_retval = nullptr;                                                         \
   return NS_OK;                                                               \
 }                                                                             \
                                                                               \
 NS_IMETHODIMP                                                                 \
-_class::GetContractID(char** _contractID)                                     \
+_class::GetContractID(nsACString& _contractID)                                \
 {                                                                             \
-  *_contractID = nullptr;                                                     \
+  _contractID.SetIsVoid(true);                                                \
   return NS_OK;                                                               \
 }                                                                             \
                                                                               \
 NS_IMETHODIMP                                                                 \
-_class::GetClassDescription(char** _classDescription)                         \
+_class::GetClassDescription(nsACString& _classDescription)                    \
 {                                                                             \
-  *_classDescription = nullptr;                                               \
+  _classDescription.SetIsVoid(true);                                          \
   return NS_OK;                                                               \
 }                                                                             \
                                                                               \
 NS_IMETHODIMP                                                                 \
 _class::GetClassID(nsCID** _classID)                                          \
 {                                                                             \
   *_classID = nullptr;                                                        \
   return NS_OK;                                                               \

--- a/xpcom/components/nsIClassInfo.idl
+++ b/xpcom/components/nsIClassInfo.idl
@@ -31,24 +31,24 @@ interface nsIClassInfo : nsISupports
     /**
      * Return an object to assist XPConnect in supplying JavaScript-specific
      * behavior to callers of the instance object, or null if not needed.
      */
     nsIXPCScriptable getScriptableHelper();
 
     /**
      * A contract ID through which an instance of this class can be created
-     * (or accessed as a service, if |flags & SINGLETON|), or null.
+     * (or accessed as a service, if |flags & SINGLETON|), or null/void.
      */
-    readonly attribute string   contractID;
+    readonly attribute AUTF8String contractID;
 
     /**
-     * A human readable string naming the class, or null.
+     * A human readable string naming the class, or null/void.
      */
-    readonly attribute string   classDescription;
+    readonly attribute AUTF8String classDescription;
 
     /**
      * A class ID through which an instance of this class can be created
      * (or accessed as a service, if |flags & SINGLETON|), or null.
      */
     readonly attribute nsCIDPtr classID;
 
     /**

--- a/xpcom/threads/nsThread.cpp
+++ b/xpcom/threads/nsThread.cpp
@@ -138,26 +138,26 @@ nsThreadClassInfo::GetInterfaces(uint32_
 NS_IMETHODIMP
 nsThreadClassInfo::GetScriptableHelper(nsIXPCScriptable** aResult)
 {
   *aResult = nullptr;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsThreadClassInfo::GetContractID(char** aResult)
+nsThreadClassInfo::GetContractID(nsACString& aResult)
 {
-  *aResult = nullptr;
+  aResult.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsThreadClassInfo::GetClassDescription(char** aResult)
+nsThreadClassInfo::GetClassDescription(nsACString& aResult)
 {
-  *aResult = nullptr;
+  aResult.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsThreadClassInfo::GetClassID(nsCID** aResult)
 {
   *aResult = nullptr;
   return NS_OK;

--- a/xpfe/appshell/nsWebShellWindow.cpp
+++ b/xpfe/appshell/nsWebShellWindow.cpp
@@ -409,16 +409,26 @@ nsWebShellWindow::UIResolutionChanged()
     mDocShell ? mDocShell->GetWindow() : nullptr;
   if (ourWindow) {
     MOZ_ASSERT(ourWindow->IsOuterWindow());
     ourWindow->DispatchCustomEvent(NS_LITERAL_STRING("resolutionchange"));
   }
 }
 
 void
+nsWebShellWindow::FullscreenWillChange(bool aInFullscreen)
+{
+  if (mDocShell) {
+    if (nsCOMPtr<nsPIDOMWindowOuter> ourWindow = mDocShell->GetWindow()) {
+      ourWindow->FullscreenWillChange(aInFullscreen);
+    }
+  }
+}
+
+void
 nsWebShellWindow::FullscreenChanged(bool aInFullscreen)
 {
   if (mDocShell) {
     if (nsCOMPtr<nsPIDOMWindowOuter> ourWindow = mDocShell->GetWindow()) {
       ourWindow->FinishFullscreenChange(aInFullscreen);
     }
   }
 }

--- a/xpfe/appshell/nsWebShellWindow.h
+++ b/xpfe/appshell/nsWebShellWindow.h
@@ -53,16 +53,17 @@ public:
   // nsIWidgetListener
   virtual nsIXULWindow* GetXULWindow() override { return this; }
   virtual nsIPresShell* GetPresShell() override;
   virtual bool WindowMoved(nsIWidget* aWidget, int32_t x, int32_t y) override;
   virtual bool WindowResized(nsIWidget* aWidget, int32_t aWidth, int32_t aHeight) override;
   virtual bool RequestWindowClose(nsIWidget* aWidget) override;
   virtual void SizeModeChanged(nsSizeMode sizeMode) override;
   virtual void UIResolutionChanged() override;
+  virtual void FullscreenWillChange(bool aInFullscreen) override;
   virtual void FullscreenChanged(bool aInFullscreen) override;
   virtual void OcclusionStateChanged(bool aIsFullyOccluded) override;
   virtual void OSToolbarButtonPressed() override;
   virtual bool ZLevelChanged(bool aImmediate, nsWindowZ *aPlacement,
                              nsIWidget* aRequestBelow, nsIWidget** aActualBelow) override;
   virtual void WindowActivated() override;
   virtual void WindowDeactivated() override;