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

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

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

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

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

deleted file mode 100644
--- a/toolkit/locales/en-US/chrome/mozapps/extensions/newaddon.dtd
+++ /dev/null
@@ -1,15 +0,0 @@
-<!-- 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/. -->
-
-<!ENTITY title           "Install Add-on">
-<!ENTITY intro           "Another program on your computer would like to modify
-                          &brandShortName; with the following add-on:">
-<!ENTITY warning         "Install add-ons only from authors whom you trust.">
-<!ENTITY allow           "Allow this installation">
-<!ENTITY later           "You can always change your mind at any time by going
-                          to the Add-ons Manager.">
-<!ENTITY continue        "Continue">
-<!ENTITY restartMessage  "You must restart &brandShortName; to finish installing this add-on.">
-<!ENTITY restartButton   "Restart &brandShortName;">
-<!ENTITY cancelButton    "Cancel">

deleted file mode 100644
--- a/toolkit/locales/en-US/chrome/mozapps/extensions/newaddon.properties
+++ /dev/null
@@ -1,10 +0,0 @@
-# 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/.
-
-#LOCALIZATION NOTE (name) %1$S is the add-on name, %2$S is the add-on version
-name=%1$S %2$S
-#LOCALIZATION NOTE (author) %S is the author of the add-on
-author=By %S
-#LOCALIZATION NOTE (location) %S is the path the add-on is installed in
-location=Location: %S

--- a/toolkit/locales/jar.mn
+++ b/toolkit/locales/jar.mn
@@ -90,18 +90,16 @@
   locale/@AB_CD@/mozapps/downloads/unknownContentType.dtd         (%chrome/mozapps/downloads/unknownContentType.dtd)
   locale/@AB_CD@/mozapps/downloads/settingsChange.dtd             (%chrome/mozapps/downloads/settingsChange.dtd)
   locale/@AB_CD@/mozapps/downloads/downloads.properties           (%chrome/mozapps/downloads/downloads.properties)
   locale/@AB_CD@/mozapps/extensions/extensions.dtd                (%chrome/mozapps/extensions/extensions.dtd)
 #ifndef MOZ_FENNEC
   locale/@AB_CD@/mozapps/extensions/extensions.properties         (%chrome/mozapps/extensions/extensions.properties)
   locale/@AB_CD@/mozapps/extensions/blocklist.dtd                 (%chrome/mozapps/extensions/blocklist.dtd)
   locale/@AB_CD@/mozapps/extensions/update.properties             (%chrome/mozapps/extensions/update.properties)
-  locale/@AB_CD@/mozapps/extensions/newaddon.dtd                  (%chrome/mozapps/extensions/newaddon.dtd)
-  locale/@AB_CD@/mozapps/extensions/newaddon.properties           (%chrome/mozapps/extensions/newaddon.properties)
 #endif
   locale/@AB_CD@/mozapps/handling/handling.dtd                    (%chrome/mozapps/handling/handling.dtd)
   locale/@AB_CD@/mozapps/handling/handling.properties             (%chrome/mozapps/handling/handling.properties)
   locale/@AB_CD@/mozapps/preferences/changemp.dtd                 (%chrome/mozapps/preferences/changemp.dtd)
   locale/@AB_CD@/mozapps/preferences/removemp.dtd                 (%chrome/mozapps/preferences/removemp.dtd)
   locale/@AB_CD@/mozapps/preferences/preferences.properties       (%chrome/mozapps/preferences/preferences.properties)
   locale/@AB_CD@/mozapps/profile/createProfileWizard.dtd          (%chrome/mozapps/profile/createProfileWizard.dtd)
   locale/@AB_CD@/mozapps/profile/profileSelection.properties      (%chrome/mozapps/profile/profileSelection.properties)

deleted file mode 100644
--- a/toolkit/mozapps/extensions/content/newaddon.js
+++ /dev/null
@@ -1,132 +0,0 @@
-/* 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/. */
-
-/* exported cancelClicked, continueClicked, initialize, restartClicked, unload */
-
-ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/AddonManager.jsm");
-
-var gAddon = null;
-
-// If the user enables the add-on through some other UI close this window
-var EnableListener = {
-  onEnabling(aAddon) {
-    if (aAddon.id == gAddon.id)
-      window.close();
-  }
-};
-AddonManager.addAddonListener(EnableListener);
-
-function initialize() {
-  // About URIs don't implement nsIURL so we have to find the query string
-  // manually
-  let spec = document.location.href;
-  let pos = spec.indexOf("?");
-  let query = "";
-  if (pos >= 0)
-    query = spec.substring(pos + 1);
-
-  // Just assume the query is "id=<id>"
-  let id = query.substring(3);
-  if (!id) {
-    window.location = "about:blank";
-    return;
-  }
-
-  let bundle = Services.strings.createBundle("chrome://mozapps/locale/extensions/newaddon.properties");
-
-  AddonManager.getAddonByID(id, function(aAddon) {
-    // If the add-on doesn't exist or it is already enabled or it has already
-    // been seen or it cannot be enabled then this UI is useless, just close it.
-    // This shouldn't normally happen unless session restore restores the tab.
-    if (!aAddon || !aAddon.userDisabled || aAddon.seen ||
-        !(aAddon.permissions & AddonManager.PERM_CAN_ENABLE)) {
-      window.close();
-      return;
-    }
-
-    gAddon = aAddon;
-
-    document.getElementById("addon-info").setAttribute("type", aAddon.type);
-
-    let icon = document.getElementById("icon");
-    if (aAddon.icon64URL)
-      icon.src = aAddon.icon64URL;
-    else if (aAddon.iconURL)
-      icon.src = aAddon.iconURL;
-
-    let name = bundle.formatStringFromName("name", [aAddon.name, aAddon.version],
-                                           2);
-    document.getElementById("name").value = name;
-
-    if (aAddon.creator) {
-      let creator = bundle.formatStringFromName("author", [aAddon.creator], 1);
-      document.getElementById("author").value = creator;
-    } else {
-      document.getElementById("author").hidden = true;
-    }
-
-    let uri = "getResourceURI" in aAddon ? aAddon.getResourceURI() : null;
-    let locationLabel = document.getElementById("location");
-    if (uri instanceof Ci.nsIFileURL) {
-      let location = bundle.formatStringFromName("location", [uri.file.path], 1);
-      locationLabel.value = location;
-      locationLabel.setAttribute("tooltiptext", location);
-    } else {
-      document.getElementById("location").hidden = true;
-    }
-
-    // Only mark the add-on as seen if the page actually gets focus
-    if (document.hasFocus()) {
-      aAddon.markAsSeen();
-    } else {
-      document.addEventListener("focus", () => aAddon.markAsSeen());
-    }
-
-    var event = document.createEvent("Events");
-    event.initEvent("AddonDisplayed", true, true);
-    document.dispatchEvent(event);
-  });
-}
-
-function unload() {
-  AddonManager.removeAddonListener(EnableListener);
-}
-
-function continueClicked() {
-  AddonManager.removeAddonListener(EnableListener);
-
-  if (document.getElementById("allow").checked) {
-    gAddon.userDisabled = false;
-
-    if (gAddon.pendingOperations & AddonManager.PENDING_ENABLE) {
-      document.getElementById("allow").disabled = true;
-      document.getElementById("buttonDeck").selectedPanel = document.getElementById("restartPanel");
-      return;
-    }
-  }
-
-  window.close();
-}
-
-function restartClicked() {
-  let cancelQuit = Cc["@mozilla.org/supports-PRBool;1"].
-                   createInstance(Ci.nsISupportsPRBool);
-  Services.obs.notifyObservers(cancelQuit, "quit-application-requested",
-                               "restart");
-  if (cancelQuit.data)
-    return; // somebody canceled our quit request
-
-  window.close();
-
-  Services.startup.quit(Ci.nsIAppStartup.eAttemptQuit | Ci.nsIAppStartup.eRestart);
-}
-
-function cancelClicked() {
-  gAddon.userDisabled = true;
-  AddonManager.addAddonListener(EnableListener);
-
-  document.getElementById("allow").disabled = false;
-  document.getElementById("buttonDeck").selectedPanel = document.getElementById("continuePanel");
-}

deleted file mode 100644
--- a/toolkit/mozapps/extensions/content/newaddon.xul
+++ /dev/null
@@ -1,67 +0,0 @@
-<?xml version="1.0"?>
-<!-- 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/. -->
-
-<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
-<?xml-stylesheet href="chrome://mozapps/skin/extensions/newaddon.css"?>
-
-<!DOCTYPE page [
-<!ENTITY % brandDTD SYSTEM "chrome://branding/locale/brand.dtd" >
-%brandDTD;
-<!ENTITY % newaddonDTD SYSTEM "chrome://mozapps/locale/extensions/newaddon.dtd">
-%newaddonDTD;
-]>
-
-<page xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
-      xmlns:xhtml="http://www.w3.org/1999/xhtml" title="&title;"
-      disablefastfind="true" id="addon-page" onload="initialize()"
-      onunload="unload()" role="application" align="stretch" pack="stretch">
-
-  <xhtml:link rel="shortcut icon" style="display: none"
-              href="chrome://mozapps/skin/extensions/extensionGeneric-16.svg"/>
-
-  <script type="application/javascript"
-          src="chrome://mozapps/content/extensions/newaddon.js"/>
-
-  <scrollbox id="addon-scrollbox" align="center">
-    <spacer id="spacer-start"/>
-
-    <vbox id="addon-container" class="main-content">
-      <description>&intro;</description>
-
-      <hbox id="addon-info">
-        <image id="icon"/>
-        <vbox flex="1">
-          <label id="name"/>
-          <label id="author"/>
-          <label id="location" crop="end"/>
-        </vbox>
-      </hbox>
-
-      <hbox id="warning">
-        <image id="warning-icon"/>
-        <description flex="1">&warning;</description>
-      </hbox>
-
-      <checkbox id="allow" label="&allow;"/>
-      <description id="later">&later;</description>
-
-      <deck id="buttonDeck">
-        <hbox id="continuePanel">
-          <button id="continue-button" label="&continue;"
-                  oncommand="continueClicked()"/>
-        </hbox>
-        <vbox id="restartPanel">
-          <description id="restartMessage">&restartMessage;</description>
-          <hbox id="restartPanelButtons">
-            <button id="restart-button" label="&restartButton;" oncommand="restartClicked()"/>
-            <button id="cancel-button" label="&cancelButton;" oncommand="cancelClicked()"/>
-          </hbox>
-        </vbox>
-      </deck>
-    </vbox>
-
-    <spacer id="spacer-end"/>
-  </scrollbox>
-</page>

--- a/toolkit/mozapps/extensions/jar.mn
+++ b/toolkit/mozapps/extensions/jar.mn
@@ -14,18 +14,16 @@ toolkit.jar:
   content/mozapps/extensions/blocklist.js                       (content/blocklist.js)
   content/mozapps/extensions/blocklist.css                      (content/blocklist.css)
   content/mozapps/extensions/blocklist.xml                      (content/blocklist.xml)
   content/mozapps/extensions/update.html                        (content/update.html)
   content/mozapps/extensions/update.js                          (content/update.js)
   content/mozapps/extensions/update.css                         (content/update.css)
   content/mozapps/extensions/eula.xul                           (content/eula.xul)
   content/mozapps/extensions/eula.js                            (content/eula.js)
-  content/mozapps/extensions/newaddon.xul                       (content/newaddon.xul)
-  content/mozapps/extensions/newaddon.js                        (content/newaddon.js)
   content/mozapps/extensions/pluginPrefs.xul                    (content/pluginPrefs.xul)
   content/mozapps/extensions/pluginPrefs.js                     (content/pluginPrefs.js)
   content/mozapps/extensions/OpenH264-license.txt               (content/OpenH264-license.txt)
 #endif
   content/mozapps/xpinstall/xpinstallConfirm.xul                (content/xpinstallConfirm.xul)
   content/mozapps/xpinstall/xpinstallConfirm.js                 (content/xpinstallConfirm.js)
   content/mozapps/xpinstall/xpinstallConfirm.css                (content/xpinstallConfirm.css)
   content/mozapps/xpinstall/xpinstallItem.xml                   (content/xpinstallItem.xml)

--- a/toolkit/mozapps/extensions/test/browser/browser.ini
+++ b/toolkit/mozapps/extensions/test/browser/browser.ini
@@ -70,17 +70,16 @@ skip-if = os == 'linux' && !debug # Bug 
 [browser_inlinesettings_browser.js]
 [browser_installssl.js]
 [browser_langpack_signing.js]
 [browser_legacy.js]
 [browser_legacy_pre57.js]
 [browser_legacy_themes.js]
 [browser_list.js]
 [browser_manualupdates.js]
-[browser_newaddon.js]
 [browser_pluginprefs.js]
 [browser_pluginprefs_is_not_disabled.js]
 skip-if = buildapp == 'mulet'
 [browser_plugin_enabled_state_locked.js]
 [browser_recentupdates.js]
 [browser_sorting.js]
 [browser_sorting_plugins.js]
 [browser_tabsettings.js]

deleted file mode 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_newaddon.js
+++ /dev/null
@@ -1,230 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/publicdomain/zero/1.0/
- */
-
-// Tests the new add-on tab
-
-var gProvider;
-
-function loadPage(aURL, aCallback, aBackground = false) {
-  let tab = BrowserTestUtils.addTab(gBrowser);
-  if (!aBackground)
-    gBrowser.selectedTab = tab;
-  let browser = tab.linkedBrowser;
-  browser.loadURI(aURL);
-  browser.addEventListener("AddonDisplayed", function(event) {
-    aCallback(tab);
-  }, {once: true});
-}
-
-function test() {
-  waitForExplicitFinish();
-
-  gProvider = new MockProvider();
-
-  gProvider.createAddons([{
-    id: "addon1@tests.mozilla.org",
-    name: "Test 1",
-    version: "5.3",
-    userDisabled: true,
-    seen: false,
-    operationsRequiringRestart: AddonManager.OP_NEEDS_RESTART_NONE
-  }, {
-    id: "addon2@tests.mozilla.org",
-    name: "Test 2",
-    version: "7.1",
-    creator: "Dave Townsend",
-    userDisabled: true,
-    seen: false
-  }]);
-
-  run_next_test();
-}
-
-function end_test() {
-  finish();
-}
-
-// Tests that ignoring a restartless add-on works
-add_test(function() {
-  loadPage("about:newaddon?id=addon1@tests.mozilla.org", function(aTab) {
-    var doc = aTab.linkedBrowser.contentDocument;
-    is(doc.getElementById("name").value, "Test 1 5.3", "Should say the right name");
-
-    is_element_hidden(doc.getElementById("author"), "Should be no author displayed");
-    is_element_hidden(doc.getElementById("location"), "Should be no location displayed");
-
-    is(doc.getElementById("buttonDeck").selectedPanel, doc.getElementById("continuePanel"),
-       "Should be showing the right buttons");
-
-    AddonManager.getAddonByID("addon1@tests.mozilla.org", function(aAddon) {
-      ok(aAddon.seen, "Add-on should have been marked as seen");
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("continue-button"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      is(gBrowser.tabs.length, 1, "Page should have been closed");
-
-      ok(aAddon.userDisabled, "Add-on should not have been enabled");
-
-      ok(!aAddon.isActive, "Add-on should not be running");
-
-      aAddon.seen = false;
-      run_next_test();
-    });
-  });
-});
-
-// Tests that enabling a restartless add-on works
-add_test(function() {
-  loadPage("about:newaddon?id=addon1@tests.mozilla.org", function(aTab) {
-    var doc = aTab.linkedBrowser.contentDocument;
-    is(doc.getElementById("name").value, "Test 1 5.3", "Should say the right name");
-
-    is_element_hidden(doc.getElementById("author"), "Should be no author displayed");
-    is_element_hidden(doc.getElementById("location"), "Should be no location displayed");
-
-    is(doc.getElementById("buttonDeck").selectedPanel, doc.getElementById("continuePanel"),
-       "Should be showing the right buttons");
-
-    AddonManager.getAddonByID("addon1@tests.mozilla.org", function(aAddon) {
-      ok(aAddon.seen, "Add-on should have been marked as seen");
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("allow"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("continue-button"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      is(gBrowser.tabs.length, 1, "Page should have been closed");
-
-      ok(!aAddon.userDisabled, "Add-on should now have been enabled");
-
-      ok(aAddon.isActive, "Add-on should now be running");
-
-      aAddon.userDisabled = true;
-      aAddon.seen = false;
-      run_next_test();
-    });
-  });
-});
-
-// Tests that ignoring a non-restartless add-on works
-add_test(function() {
-  loadPage("about:newaddon?id=addon2@tests.mozilla.org", function(aTab) {
-    var doc = aTab.linkedBrowser.contentDocument;
-    is(doc.getElementById("name").value, "Test 2 7.1", "Should say the right name");
-
-    is_element_visible(doc.getElementById("author"), "Should be an author displayed");
-    is(doc.getElementById("author").value, "By Dave Townsend", "Should have the right author");
-    is_element_hidden(doc.getElementById("location"), "Should be no location displayed");
-
-    is(doc.getElementById("buttonDeck").selectedPanel, doc.getElementById("continuePanel"),
-       "Should be showing the right buttons");
-
-    AddonManager.getAddonByID("addon2@tests.mozilla.org", function(aAddon) {
-      ok(aAddon.seen, "Add-on should have been marked as seen");
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("continue-button"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      is(gBrowser.tabs.length, 1, "Page should have been closed");
-
-      ok(aAddon.userDisabled, "Add-on should not have been enabled");
-
-      ok(!aAddon.isActive, "Add-on should not be running");
-
-      aAddon.seen = false;
-      run_next_test();
-    });
-  });
-});
-
-// Tests that enabling a non-restartless add-on works
-add_test(function() {
-  loadPage("about:newaddon?id=addon2@tests.mozilla.org", function(aTab) {
-    var doc = aTab.linkedBrowser.contentDocument;
-    is(doc.getElementById("name").value, "Test 2 7.1", "Should say the right name");
-
-    is_element_visible(doc.getElementById("author"), "Should be an author displayed");
-    is(doc.getElementById("author").value, "By Dave Townsend", "Should have the right author");
-    is_element_hidden(doc.getElementById("location"), "Should be no location displayed");
-
-    is(doc.getElementById("buttonDeck").selectedPanel, doc.getElementById("continuePanel"),
-       "Should be showing the right buttons");
-
-    AddonManager.getAddonByID("addon2@tests.mozilla.org", function(aAddon) {
-      ok(aAddon.seen, "Add-on should have been marked as seen");
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("allow"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("continue-button"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      is(doc.getElementById("buttonDeck").selectedPanel, doc.getElementById("restartPanel"),
-         "Should be showing the right buttons");
-
-      ok(!aAddon.userDisabled, "Add-on should now have been enabled");
-
-      ok(!aAddon.isActive, "Add-on should not be running");
-
-      ok(doc.getElementById("allow").disabled, "Should have disabled checkbox");
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("cancel-button"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      is(doc.getElementById("buttonDeck").selectedPanel, doc.getElementById("continuePanel"),
-         "Should be showing the right buttons");
-
-      ok(!doc.getElementById("allow").disabled, "Should have enabled checkbox");
-
-      ok(aAddon.userDisabled, "Add-on should not have been enabled");
-
-      ok(!aAddon.isActive, "Add-on should not be running");
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("allow"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      EventUtils.synthesizeMouseAtCenter(doc.getElementById("continue-button"),
-                                         {}, aTab.linkedBrowser.contentWindow);
-
-      ok(aAddon.userDisabled, "Add-on should not have been enabled");
-
-      ok(!aAddon.isActive, "Add-on should not be running");
-
-      is(gBrowser.tabs.length, 1, "Page should have been closed");
-
-      aAddon.seen = false;
-      run_next_test();
-    });
-  });
-});
-
-// Tests that opening the page in the background doesn't mark as seen
-add_test(function() {
-  loadPage("about:newaddon?id=addon1@tests.mozilla.org", function(aTab) {
-    var doc = aTab.linkedBrowser.contentDocument;
-    is(doc.getElementById("name").value, "Test 1 5.3", "Should say the right name");
-
-    is_element_hidden(doc.getElementById("author"), "Should be no author displayed");
-    is_element_hidden(doc.getElementById("location"), "Should be no location displayed");
-
-    is(doc.getElementById("buttonDeck").selectedPanel, doc.getElementById("continuePanel"),
-       "Should be showing the right buttons");
-
-    AddonManager.getAddonByID("addon1@tests.mozilla.org", function(aAddon) {
-      ok(!aAddon.seen, "Add-on should not have been marked as seen.");
-
-      gBrowser.selectedTab = aTab;
-
-      waitForFocus(function() {
-        ok(aAddon.seen, "Add-on should have been marked as seen after focusing the tab.");
-
-        gBrowser.removeTab(aTab);
-
-        run_next_test();
-      }, aTab.linkedBrowser.contentWindow);
-    });
-  }, true);
-});

deleted file mode 100644
--- a/toolkit/themes/linux/mozapps/extensions/newaddon.css
+++ /dev/null
@@ -1,5 +0,0 @@
-/* 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 ../../../shared/extensions/newaddon.inc.css

--- a/toolkit/themes/linux/mozapps/jar.mn
+++ b/toolkit/themes/linux/mozapps/jar.mn
@@ -1,16 +1,15 @@
 # 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/.
 
 toolkit.jar:
 #include ../../shared/mozapps.inc.mn
 * skin/classic/mozapps/extensions/extensions.css           (extensions/extensions.css)
-* skin/classic/mozapps/extensions/newaddon.css             (extensions/newaddon.css)
   skin/classic/mozapps/extensions/heart.png                (extensions/heart.png)
   skin/classic/mozapps/profile/profileicon.png             (profile/profileicon.png)
   skin/classic/mozapps/update/updates.css                  (update/updates.css)
 
 #if MOZ_BUILD_APP == browser
 [browser/extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
 #elif MOZ_SEPARATE_MANIFEST_FOR_THEME_OVERRIDES
 [extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:

deleted file mode 100644
--- a/toolkit/themes/osx/mozapps/extensions/newaddon.css
+++ /dev/null
@@ -1,5 +0,0 @@
-/* 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 ../../../shared/extensions/newaddon.inc.css

--- a/toolkit/themes/osx/mozapps/jar.mn
+++ b/toolkit/themes/osx/mozapps/jar.mn
@@ -10,17 +10,16 @@ toolkit.jar:
   skin/classic/mozapps/extensions/rating-won.png                  (extensions/rating-won.png)
   skin/classic/mozapps/extensions/rating-not-won.png              (extensions/rating-not-won.png)
   skin/classic/mozapps/extensions/cancel.png                      (extensions/cancel.png)
   skin/classic/mozapps/extensions/toolbarbutton-dropmarker.png    (extensions/toolbarbutton-dropmarker.png)
   skin/classic/mozapps/extensions/heart.png                       (extensions/heart.png)
 * skin/classic/mozapps/extensions/extensions.css                  (extensions/extensions.css)
   skin/classic/mozapps/extensions/eula.css                        (extensions/eula.css)
   skin/classic/mozapps/extensions/blocklist.css                   (extensions/blocklist.css)
-* skin/classic/mozapps/extensions/newaddon.css                    (extensions/newaddon.css)
   skin/classic/mozapps/plugins/pluginHelp-16.png                  (plugins/pluginHelp-16.png)
   skin/classic/mozapps/profile/profileicon.png                    (profile/profileicon.png)
   skin/classic/mozapps/profile/profileSelection.css               (profile/profileSelection.css)
   skin/classic/mozapps/profile/profileicon-selected.png           (profile/profileicon-selected.png)
   skin/classic/mozapps/update/buttons.png                         (update/buttons.png)
 * skin/classic/mozapps/update/updates.css                         (update/updates.css)
   skin/classic/mozapps/xpinstall/xpinstallConfirm.css             (extensions/xpinstallConfirm.css)
   skin/classic/mozapps/handling/handling.css                      (handling/handling.css)

deleted file mode 100644
--- a/toolkit/themes/shared/extensions/newaddon.inc.css
+++ /dev/null
@@ -1,114 +0,0 @@
-%if 0
-/* 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/. */
-%endif
-@import url("chrome://global/skin/in-content/common.css");
-
-#addon-page {
-  font-size: 1.1em;
-}
-
-#addon-scrollbox {
-  overflow: auto;
-  -moz-box-orient: vertical;
-  -moz-box-flex: 1;
-}
-
-#spacer-start {
-  -moz-box-flex: 1;
-}
-
-#spacer-end {
-  -moz-box-flex: 3;
-}
-
-#addon-container {
-  overflow: visible;
-  max-width: 800px;
-  margin: 20px;
-  padding: 30px 90px;
-}
-
-#addon-info {
-  -moz-box-align: start;
-  margin: 25px 10px;
-}
-
-#icon {
-  margin-top: 8px;
-  margin-inline-end: 10px;
-  max-width: 64px;
-  max-height: 64px;
-  list-style-image: url("chrome://mozapps/skin/extensions/extensionGeneric.svg");
-}
-
-.addon-info[type="theme"] #icon {
-  list-style-image: url("chrome://mozapps/skin/extensions/themeGeneric.svg");
-}
-
-.addon-info[type="locale"] #icon {
-  list-style-image: url("chrome://mozapps/skin/extensions/localeGeneric.svg");
-}
-
-.addon-info[type="plugin"] #icon {
-  list-style-image: url("chrome://mozapps/skin/plugins/pluginGeneric.svg");
-}
-
-.addon-info[type="dictionary"] #icon {
-  list-style-image: url("chrome://mozapps/skin/extensions/dictionaryGeneric.svg");
-}
-
-#name {
-  font-size: 130%;
-}
-
-#author {
-  color: GrayText;
-}
-
-#location {
-  color: GrayText;
-}
-
-#warning {
-  margin-bottom: 25px;
-  -moz-box-align: start;
-}
-
-#warning-icon {
-  list-style-image: url("chrome://mozapps/skin/extensions/alerticon-warning.svg");
-  width: 16px;
-  height: 16px;
-  margin-top: 5px;
-  margin-inline-end: 5px;
-}
-
-#allow {
-  margin-inline-start: 84px;
-  margin-bottom: 20px;
-}
-
-#buttonDeck {
-  margin-top: 25px;
-  -moz-box-align: stretch;
-}
-
-#continuePanel {
-  -moz-box-pack: end;
-  -moz-box-align: end;
-}
-
-#restartPanel {
-  -moz-box-pack: end;
-  -moz-box-align: stretch;
-}
-
-#restartPanelButtons {
-  margin-top: 25px;
-  -moz-box-pack: end;
-}
-
-#later {
-  color: GrayText;
-}

deleted file mode 100644
--- a/toolkit/themes/windows/mozapps/extensions/newaddon.css
+++ /dev/null
@@ -1,5 +0,0 @@
-/* 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 ../../../shared/extensions/newaddon.inc.css

--- a/toolkit/themes/windows/mozapps/jar.mn
+++ b/toolkit/themes/windows/mozapps/jar.mn
@@ -1,17 +1,16 @@
 # 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/.
 
 toolkit.jar:
 #include ../../shared/mozapps.inc.mn
 * skin/classic/mozapps/extensions/extensions.css             (extensions/extensions.css)
   skin/classic/mozapps/extensions/heart.png                  (extensions/heart.png)
-* skin/classic/mozapps/extensions/newaddon.css               (extensions/newaddon.css)
   skin/classic/mozapps/profile/profileicon.png               (profile/profileicon.png)
   skin/classic/mozapps/update/updates.css                    (update/updates.css)
 
 #if MOZ_BUILD_APP == browser
 [browser/extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
 #elif MOZ_SEPARATE_MANIFEST_FOR_THEME_OVERRIDES
 [extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
 #endif