diff --git a/browser/base/content/safeMode.css b/browser/base/content/safeMode.css
index 4f093a452f..78be86e564 100644
--- a/browser/base/content/safeMode.css
+++ b/browser/base/content/safeMode.css
@@ -6,3 +6,11 @@
   font-weight: bold;
 }
 
+/* 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/. */
+
+#resetProfileFooter {
+  font-weight: bold;
+}
+
diff --git a/browser/base/content/safeMode.js b/browser/base/content/safeMode.js
index e1e5c72859..5df931326e 100644
--- a/browser/base/content/safeMode.js
+++ b/browser/base/content/safeMode.js
@@ -2,127 +2,85 @@
    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/. */
 
-const Cc = Components.classes,
-      Ci = Components.interfaces,
-      Cu = Components.utils;
-      
-Cu.import("resource://gre/modules/AddonManager.jsm");
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cu = Components.utils;
+
+const appStartup = Services.startup;
+
+Cu.import("resource://gre/modules/ResetProfile.jsm");
+
+let defaultToReset = false;
 
 function restartApp() {
-  let appStartup = Cc["@mozilla.org/toolkit/app-startup;1"]
-                      .getService(Ci.nsIAppStartup);
-  appStartup.quit(Ci.nsIAppStartup.eForceQuit |  Ci.nsIAppStartup.eRestart);
+  appStartup.quit(appStartup.eForceQuit | appStartup.eRestart);
 }
 
-function clearAllPrefs() {
-  var prefService = Cc["@mozilla.org/preferences-service;1"]
-                       .getService(Ci.nsIPrefService);
-  prefService.resetUserPrefs();
-
-  // Remove the pref-overrides dir, if it exists
-  try {
-    var fileLocator = Cc["@mozilla.org/file/directory_service;1"]
-                         .getService(Ci.nsIProperties);
-    const NS_APP_PREFS_OVERRIDE_DIR = "PrefDOverride";
-    var prefOverridesDir = fileLocator.get(NS_APP_PREFS_OVERRIDE_DIR,
-                                           Ci.nsIFile);
-    prefOverridesDir.remove(true);
-  } catch (ex) {
-    Components.utils.reportError(ex);
-  }
+function resetProfile() {
+  // Set the reset profile environment variable.
+  let env = Cc["@mozilla.org/process/environment;1"]
+              .getService(Ci.nsIEnvironment);
+  env.set("MOZ_RESET_PROFILE_RESTART", "1");
 }
 
-function restoreDefaultBookmarks() {
-  var prefBranch  = Cc["@mozilla.org/preferences-service;1"]
-                       .getService(Ci.nsIPrefBranch);
-  prefBranch.setBoolPref("browser.bookmarks.restore_default_bookmarks", true);
-}
-
-function deleteLocalstore() {
-  const nsIDirectoryServiceContractID = "@mozilla.org/file/directory_service;1";
-  const nsIProperties = Ci.nsIProperties;
-  var directoryService = Cc[nsIDirectoryServiceContractID]
-                            .getService(nsIProperties);
-  // Local store file
-  var localstoreFile = directoryService.get("LStoreS", Components.interfaces.nsIFile);
-  // XUL store file
-  var xulstoreFile = directoryService.get("ProfD", Components.interfaces.nsIFile);
-  xulstoreFile.append("xulstore.json");
-  try {
-    xulstoreFile.remove(false);
-    if (localstoreFile.exists()) {
-      localstoreFile.remove(false);
-    }
-  } catch(e) {
-    Components.utils.reportError(e);
-  }
-}
-
-function disableAddons() {
-  AddonManager.getAllAddons(function(aAddons) {
-    aAddons.forEach(function(aAddon) {
-      if (aAddon.type == "theme") {
-        // Setting userDisabled to false on the default theme activates it,
-        // disables all other themes and deactivates the applied persona, if
-        // any.
-        const DEFAULT_THEME_ID = "{972ce4c6-7e08-4474-a285-3208198ce6fd}";
-        if (aAddon.id == DEFAULT_THEME_ID)
-          aAddon.userDisabled = false;
-      }
-      else {
-        aAddon.userDisabled = true;
-      }
-    });
-
-    restartApp();
-  });
-}
-
-function restoreDefaultSearchEngines() {
-  var searchService = Cc["@mozilla.org/browser/search-service;1"]
-                         .getService(Ci.nsIBrowserSearchService);
-
-  searchService.restoreDefaultEngines();
-}
-
-function onOK() {
-  try {
-    if (document.getElementById("resetUserPrefs").checked)
-      clearAllPrefs();
-    if (document.getElementById("deleteBookmarks").checked)
-      restoreDefaultBookmarks();
-    if (document.getElementById("resetToolbars").checked)
-      deleteLocalstore();
-    if (document.getElementById("restoreSearch").checked)
-      restoreDefaultSearchEngines();
-    if (document.getElementById("disableAddons").checked) {
-      disableAddons();
-      // disableAddons will asynchronously restart the application
-      return false;
-    }
-  } catch(e) {
-  }
-
+function showResetDialog() {
+  // Prompt the user to confirm the reset.
+  let retVals = {
+    reset: false,
+  };
+  window.openDialog("chrome://global/content/resetProfile.xul", null,
+                    "chrome,modal,centerscreen,titlebar,dialog=yes", retVals);
+  if (!retVals.reset)
+    return;
+  resetProfile();
   restartApp();
-  return false;
+}
+
+function onDefaultButton() {
+  if (defaultToReset) {
+    // Restart to reset the profile.
+    resetProfile();
+    restartApp();
+    // Return false to prevent starting into safe mode while restarting.
+    return false;
+  } else {
+    // Continue in safe mode. No restart needed.
+    return true;
+  }
 }
 
 function onCancel() {
-  let appStartup = Cc["@mozilla.org/toolkit/app-startup;1"]
-                      .getService(Ci.nsIAppStartup);
-  appStartup.quit(Ci.nsIAppStartup.eForceQuit);
+  appStartup.quit(appStartup.eForceQuit);
+}
+
+function onExtra1() {
+  if (defaultToReset) {
+    // Continue in safe mode
+    window.close();
+    return true;
+  } else {
+    // The reset dialog will handle starting the reset process if the user confirms.
+    showResetDialog();
+  }
+  return false;
 }
 
 function onLoad() {
-  document.getElementById("tasks")
-          .addEventListener("CheckboxStateChange", UpdateOKButtonState, false);
-}
-
-function UpdateOKButtonState() {
-  document.documentElement.getButton("accept").disabled = 
-    !document.getElementById("resetUserPrefs").checked &&
-    !document.getElementById("deleteBookmarks").checked &&
-    !document.getElementById("resetToolbars").checked &&
-    !document.getElementById("disableAddons").checked &&
-    !document.getElementById("restoreSearch").checked;
+  let dialog = document.documentElement;
+  if (appStartup.automaticSafeModeNecessary) {
+    document.getElementById("autoSafeMode").hidden = false;
+    document.getElementById("safeMode").hidden = true;
+    if (ResetProfile.resetSupported()) {
+      document.getElementById("resetProfile").hidden = false;
+    } else {
+      // Hide the reset button is it's not supported.
+      document.documentElement.getButton("extra1").hidden = true;
+    }
+  } else {
+    if (!ResetProfile.resetSupported()) {
+      // Hide the reset button and text if it's not supported.
+      document.documentElement.getButton("extra1").hidden = true;
+      document.getElementById("resetProfileInstead").hidden = true;
+    }
+  }
 }
diff --git a/browser/base/content/safeMode.xul b/browser/base/content/safeMode.xul
index 656df6eaf8..a261a68a55 100644
--- a/browser/base/content/safeMode.xul
+++ b/browser/base/content/safeMode.xul
@@ -5,51 +5,49 @@ 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/. -->
 
+
 <!DOCTYPE prefwindow [
 <!ENTITY % brandDTD SYSTEM "chrome://branding/locale/brand.dtd" >
 %brandDTD;
 <!ENTITY % safeModeDTD SYSTEM "chrome://browser/locale/safeMode.dtd" >
 %safeModeDTD;
-<!ENTITY % browserDTD SYSTEM "chrome://browser/locale/browser.dtd" >
-%browserDTD;
+<!ENTITY % resetProfileDTD SYSTEM "chrome://global/locale/resetProfile.dtd" >
+%resetProfileDTD;
 ]>
 
 <?xml-stylesheet href="chrome://global/skin/"?>
+<?xml-stylesheet href="chrome://browser/content/safeMode.css"?>
 
 <dialog id="safeModeDialog"
             xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
             title="&safeModeDialog.title;"
-            buttons="accept,cancel,extra1"
-            buttonlabelaccept="&changeAndRestartButton.label;"
-#ifdef XP_WIN
-            buttonlabelcancel="&quitApplicationCmdWin.label;"
-#else
-            buttonlabelcancel="&quitApplicationCmd.label;"
-#endif
-            buttonlabelextra1="&continueButton.label;"
-            width="&window.width;"
-            ondialogaccept="return onOK()"
-            ondialogcancel="onCancel()"
-            ondialogextra1="window.close()"
-            onload="onLoad();"
-            buttondisabledaccept="true">
+            buttons="accept,extra1"
+            buttonlabelaccept="&startSafeMode.label;"
+            buttonlabelextra1="&refreshProfile.label;"
+            maxwidth="&window.maxWidth;"
+            ondialogaccept="return onDefaultButton()"
+            ondialogcancel="onCancel();"
+            ondialogextra1="return onExtra1()"
+            onload="onLoad()">
 
+  <script type="application/javascript" src="chrome://global/content/resetProfile.js"/>
   <script type="application/javascript" src="chrome://browser/content/safeMode.js"/>
 
-  <stringbundle id="preferencesBundle" src="chrome://browser/locale/preferences/preferences.properties"/>
-
-  <description>&safeModeDescription.label;</description>
-
-  <separator class="thin"/>
-
-  <label value="&safeModeDescription2.label;"/>
-  <vbox id="tasks">
-    <checkbox id="disableAddons"  label="&disableAddons.label;"  accesskey="&disableAddons.accesskey;"/>
-    <checkbox id="resetToolbars"  label="&resetToolbars.label;"  accesskey="&resetToolbars.accesskey;"/>
-    <checkbox id="deleteBookmarks" label="&deleteBookmarks.label;" accesskey="&deleteBookmarks.accesskey;"/>
-    <checkbox id="resetUserPrefs" label="&resetUserPrefs.label;" accesskey="&resetUserPrefs.accesskey;"/>
-    <checkbox id="restoreSearch"  label="&restoreSearch.label;"  accesskey="&restoreSearch.accesskey;"/>
+  <vbox id="autoSafeMode" hidden="true">
+    <description>&autoSafeModeDescription3.label;</description>
   </vbox>
-     
+
+  <vbox id="safeMode">
+    <label>&safeModeDescription3.label;</label>
+    <separator class="thin"/>
+    <label>&safeModeDescription4.label;</label>
+    <separator class="thin"/>
+    <label id="resetProfileInstead">&refreshProfileInstead.label;</label>
+  </vbox>
+
+  <vbox id="resetProfile" hidden="true">
+    <label id="resetProfileInstead">&refreshProfileInstead.label;</label>
+  </vbox>
+
   <separator class="thin"/>
 </dialog>
diff --git a/browser/base/content/tabbrowser.xml b/browser/base/content/tabbrowser.xml
index ed35c5ad9a..3b35eb7902 100644
--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -1447,11 +1447,6 @@
 
             var uriIsAboutBlank = !aURI || aURI == "about:blank";
 
-            if (!aURI || isBlankPageURL(aURI))
-              t.setAttribute("label", this.mStringBundle.getString("tabs.emptyTabTitle"));
-            else
-              t.setAttribute("label", aURI);
-
             t.setAttribute("crop", "end");
             t.setAttribute("validate", "never"); //PMed
             t.setAttribute("onerror", "this.removeAttribute('image');");
@@ -1559,6 +1554,14 @@
             // initialized by this point.
             this.mPanelContainer.appendChild(notificationbox);
 
+            // We've waited until the tab is in the DOM to set the label. This
+            // allows the TabLabelModified event to be properly dispatched.
+            if (!aURI || isBlankPageURL(aURI)) {
+              t.label = this.mStringBundle.getString("tabs.emptyTabTitle");
+            } else {
+              t.label = aURI;
+            }
+
             this.tabContainer.updateVisibility();
 
             // wire up a progress listener for the new browser object.
@@ -3401,8 +3404,7 @@
           this._closeWindowWithLastTab = Services.prefs.getBoolPref("browser.tabs.closeWindowWithLastTab");
 
           var tab = this.firstChild;
-          tab.setAttribute("label",
-                           this.tabbrowser.mStringBundle.getString("tabs.emptyTabTitle"));
+          tab.label = this.tabbrowser.mStringBundle.getString("tabs.emptyTabTitle");
           tab.setAttribute("crop", "end");
           tab.setAttribute("onerror", "this.removeAttribute('image');");
           this.adjustTabstrip();
@@ -4714,7 +4716,8 @@
                      role="presentation"
                      anonid="tab-icon"/>
           <xul:label flex="1"
-                     xbl:inherits="value=label,crop,accesskey,fadein,pinned,selected"
+                     anonid="tab-label"
+                     xbl:inherits="value=visibleLabel,crop,accesskey,fadein,pinned,selected"
                      class="tab-text tab-label"
                      role="presentation"/>
           <xul:toolbarbutton anonid="close-button"
@@ -4725,6 +4728,32 @@
     </content>
 
     <implementation>
+      <property name="label">
+        <getter>
+          return this.getAttribute("label");
+        </getter>
+        <setter>
+          this.setAttribute("label", val);
+          let event = new CustomEvent("TabLabelModified", {
+            bubbles: true,
+            cancelable: true
+          });
+          this.dispatchEvent(event);
+
+          // Let listeners prevent synchronizing the actual label to the
+          // visible label (allowing them to override the visible label).
+          if (!event.defaultPrevented)
+            this.visibleLabel = val;
+        </setter>
+      </property>
+      <property name="visibleLabel">
+        <getter>
+          return this.getAttribute("visibleLabel");
+        </getter>
+        <setter>
+          this.setAttribute("visibleLabel", val);
+        </setter>
+      </property>
       <property name="pinned" readonly="true">
         <getter>
           return this.getAttribute("pinned") == "true";
diff --git a/browser/base/content/test/general/browser_visibleLabel.js b/browser/base/content/test/general/browser_visibleLabel.js
new file mode 100644
index 0000000000..c34b399af0
--- /dev/null
+++ b/browser/base/content/test/general/browser_visibleLabel.js
@@ -0,0 +1,94 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* Tests:
+ *   verify that the visibleLabel attribute works
+ *   verify the TabLabelModified event works for both existing and new tabs
+ */
+
+function test() {
+  waitForExplicitFinish();
+  registerCleanupFunction(function() {
+    gBrowser.removeCurrentTab({animate: false});
+  });
+  let tab = gBrowser.selectedTab = gBrowser.addTab("about:blank",
+                                                   {skipAnimation: true});
+  tab.linkedBrowser.addEventListener("load", function onLoad(event) {
+    event.currentTarget.removeEventListener("load", onLoad, true);
+    executeSoon(afterLoad);
+  }, true);
+}
+
+function afterLoad() {
+  let tab = gBrowser.selectedTab;
+  let xulLabel = document.getAnonymousElementByAttribute(tab, "anonid",
+                                                         "tab-label");
+  // Verify we're starting out on the right foot
+  is(tab.label, "New Tab", "Initial tab label is default");
+  is(xulLabel.value, "New Tab", "Label element is default");
+  is(tab.visibleLabel, "New Tab", "visibleLabel is default");
+
+  // Check that a normal label setting works correctly
+  tab.label = "Hello, world!";
+  is(tab.label, "Hello, world!", "tab label attribute set via tab.label");
+  is(xulLabel.value, "Hello, world!", "xul:label set via tab.label");
+  is(tab.visibleLabel, "Hello, world!", "visibleLabel set via tab.label");
+
+  // Check that setting visibleLabel only affects the label element
+  tab.visibleLabel = "Goodnight, Irene";
+  is(tab.label, "Hello, world!", "Tab.label unaffected by visibleLabel setter");
+  is(xulLabel.value, "Goodnight, Irene",
+     "xul:label set by visibleLabel setter");
+  is(tab.visibleLabel, "Goodnight, Irene",
+     "visibleLabel attribute set by visibleLabel setter");
+
+  // Check that setting the label property hits everything
+  tab.label = "One more label";
+  is(tab.label, "One more label",
+     "Tab label set via label property after diverging from visibleLabel");
+  is(xulLabel.value, "One more label",
+     "xul:label set via label property after diverging from visibleLabel");
+  is(tab.visibleLabel, "One more label",
+     "visibleLabel set from label property after diverging from visibleLabel");
+
+  tab.addEventListener("TabLabelModified", overrideTabLabel, true);
+  tab.label = "This won't be the visibleLabel";
+}
+
+function overrideTabLabel(aEvent) {
+  aEvent.target.removeEventListener("TabLabelModified", overrideTabLabel, true);
+  aEvent.preventDefault();
+  aEvent.stopPropagation();
+  aEvent.target.visibleLabel = "Handler set this as the visible label";
+  executeSoon(checkTabLabelModified);
+}
+
+function checkTabLabelModified() {
+  let tab = gBrowser.selectedTab;
+  let xulLabel = document.getAnonymousElementByAttribute(tab, "anonid",
+                                                         "tab-label");
+
+  is(tab.label, "This won't be the visibleLabel",
+     "Tab label set via label property that triggered event");
+  is(xulLabel.value, "Handler set this as the visible label",
+     "xul:label set by TabLabelModified handler");
+  is(tab.visibleLabel, "Handler set this as the visible label",
+     "visibleLabel set by TabLabelModified handler");
+
+  gBrowser.removeCurrentTab({animate: false});
+  executeSoon(checkTabLabelModifiedOnNewTab);
+}
+
+function checkTabLabelModifiedOnNewTab() {
+  gBrowser.tabContainer.addEventListener("TabLabelModified",
+    handleTabLabelModifiedOnNewTab, true);
+  let tab = gBrowser.selectedTab = gBrowser.addTab("about:blank",
+                                                   {skipAnimation: true});
+}
+
+function handleTabLabelModifiedOnNewTab(aEvent) {
+  gBrowser.tabContainer.removeEventListener("TabLabelModified",
+    handleTabLabelModifiedOnNewTab, true);
+  ok(true, "Event received from new tab default being set");
+  executeSoon(finish);
+}
diff --git a/browser/components/migration/content/aboutWelcomeBack.xhtml b/browser/components/migration/content/aboutWelcomeBack.xhtml
index 7022682668..0fa76d4d87 100644
--- a/browser/components/migration/content/aboutWelcomeBack.xhtml
+++ b/browser/components/migration/content/aboutWelcomeBack.xhtml
@@ -33,7 +33,7 @@
 
       <!-- Error Title -->
       <div id="errorTitle">
-        <h1 id="errorTitleText">&welcomeback.pageTitle;</h1>
+        <h1 id="errorTitleText">&welcomeback2.pageTitle;</h1>
       </div>
 
       <!-- LONG CONTENT (the section most likely to require scrolling) -->
@@ -41,7 +41,9 @@
 
         <!-- Short Description -->
         <div id="errorShortDesc">
-          <p id="errorShortDescText">&welcomeback.pageInfo;</p>
+          <p>&welcomeback2.pageInfo1;</p>
+          <!-- Note a href in the anchor below is added by JS -->
+          <p>&welcomeback2.beforelink.pageInfo2;<a id="linkMoreTroubleshooting" target="_blank">&welcomeback2.link.pageInfo2;</a>&welcomeback2.afterlink.pageInfo2;</p>
         </div>
 
         <!-- Long Description (Note: See netError.dtd for used XHTML tags) -->
@@ -66,21 +68,9 @@
 
       <!-- Buttons -->
       <hbox xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" id="buttons">
-#ifdef XP_UNIX
-        <button id="errorCancel" label="&restorepage.closeButton;"
-                accesskey="&restorepage.close.access;"
-                oncommand="startNewSession();"/>
-        <button id="errorTryAgain" label="&restorepage.tryagainButton;"
-                accesskey="&restorepage.restore.access;"
+        <button id="errorTryAgain" label="&welcomeback2.restoreButton;"
+                accesskey="&welcomeback2.restoreButton.access;"
                 oncommand="restoreSession();"/>
-#else
-        <button id="errorTryAgain" label="&restorepage.tryagainButton;"
-                accesskey="&restorepage.restore.access;"
-                oncommand="restoreSession();"/>
-        <button id="errorCancel" label="&restorepage.closeButton;"
-                accesskey="&restorepage.close.access;"
-                oncommand="startNewSession();"/>
-#endif
       </hbox>
       <!-- holds the session data for when the tab is closed -->
       <input type="text" id="sessionData" style="display: none;"/>
diff --git a/browser/components/nsBrowserGlue.js b/browser/components/nsBrowserGlue.js
index f6a17e2eae..7da50e2395 100644
--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -611,6 +611,41 @@ BrowserGlue.prototype = {
                           nb.PRIORITY_INFO_LOW, buttons);
   },
 
+  /**
+   * Show a notification bar offering a reset if the profile has been unused for some time.
+   */
+  _resetUnusedProfileNotification: function () {
+    let win = this.getMostRecentBrowserWindow();
+    if (!win)
+      return;
+
+    Cu.import("resource://gre/modules/ResetProfile.jsm");
+    if (!ResetProfile.resetSupported())
+      return;
+
+    let productName = Services.strings
+                              .createBundle("chrome://branding/locale/brand.properties")
+                              .GetStringFromName("brandShortName");
+    let resetBundle = Services.strings
+                              .createBundle("chrome://global/locale/resetProfile.properties");
+
+    let message = resetBundle.formatStringFromName("resetUnusedProfile.message", [productName], 1);
+    let buttons = [
+      {
+        label:     resetBundle.formatStringFromName("refreshProfile.resetButton.label", [productName], 1),
+        accessKey: resetBundle.GetStringFromName("refreshProfile.resetButton.accesskey"),
+        callback: function () {
+          ResetProfile.openConfirmationDialog(win);
+        }
+      },
+    ];
+
+    let nb = win.document.getElementById("global-notificationbox");
+    nb.appendNotification(message, "reset-unused-profile",
+                          "chrome://global/skin/icons/question-16.png",
+                          nb.PRIORITY_INFO_LOW, buttons);
+  },
+
   // the first browser window has finished initializing
   _onFirstWindowLoaded: function BG__onFirstWindowLoaded(aWindow) {
 #ifdef XP_WIN
@@ -625,6 +660,15 @@ BrowserGlue.prototype = {
 #endif
 
     this._trackSlowStartup();
+
+    // Offer to reset a user's profile if it hasn't been used for 60 days.
+    const OFFER_PROFILE_RESET_INTERVAL_MS = 60 * 24 * 60 * 60 * 1000;
+    let processStartupTime = Services.startup.getStartupInfo().process;
+    let lastUse = Services.appinfo.replacedLockTime;
+    if (processStartupTime && lastUse &&
+        processStartupTime.getTime() - lastUse >= OFFER_PROFILE_RESET_INTERVAL_MS) {
+      this._resetUnusedProfileNotification();
+    }
   },
 
   /**
diff --git a/browser/components/sessionstore/RecentlyClosedTabsAndWindowsMenuUtils.jsm b/browser/components/sessionstore/RecentlyClosedTabsAndWindowsMenuUtils.jsm
index 073708deec..521b05708b 100644
--- a/browser/components/sessionstore/RecentlyClosedTabsAndWindowsMenuUtils.jsm
+++ b/browser/components/sessionstore/RecentlyClosedTabsAndWindowsMenuUtils.jsm
@@ -72,7 +72,7 @@ this.RecentlyClosedTabsAndWindowsMenuUtils = {
       let restoreAllTabs = fragment.appendChild(doc.createElementNS(kNSXUL, aTagName));
       restoreAllTabs.setAttribute("label", navigatorBundle.GetStringFromName("menuRestoreAllTabs.label"));
       restoreAllTabs.setAttribute("oncommand",
-              "for (var i = 0; i < " + closedTabs.length + "; i++) undoCloseTab(0);");
+              "for (var i = 0; i < " + closedTabs.length + "; i++) undoCloseTab();");
     }
     return fragment;
   },
diff --git a/browser/components/sessionstore/SessionSaver.jsm b/browser/components/sessionstore/SessionSaver.jsm
index 145f68a66f..8ac7461379 100644
--- a/browser/components/sessionstore/SessionSaver.jsm
+++ b/browser/components/sessionstore/SessionSaver.jsm
@@ -15,6 +15,8 @@ Cu.import("resource://gre/modules/Services.jsm", this);
 Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
 Cu.import("resource://gre/modules/TelemetryStopwatch.jsm", this);
 
+XPCOMUtils.defineLazyModuleGetter(this, "AppConstants",
+  "resource://gre/modules/AppConstants.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "console",
   "resource://gre/modules/devtools/Console.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "PrivacyFilter",
@@ -206,23 +208,23 @@ let SessionSaverInternal = {
       delete state.deferredInitialState;
     }
 
-#ifndef XP_MACOSX
-    // We want to restore closed windows that are marked with _shouldRestore.
-    // We're doing this here because we want to control this only when saving
-    // the file.
-    while (state._closedWindows.length) {
-      let i = state._closedWindows.length - 1;
+    if (AppConstants.platform != "macosx") {
+      // We want to restore closed windows that are marked with _shouldRestore.
+      // We're doing this here because we want to control this only when saving
+      // the file.
+      while (state._closedWindows.length) {
+        let i = state._closedWindows.length - 1;
 
-      if (!state._closedWindows[i]._shouldRestore) {
-        // We only need to go until _shouldRestore
-        // is falsy since we're going in reverse.
-        break;
+        if (!state._closedWindows[i]._shouldRestore) {
+          // We only need to go until _shouldRestore
+          // is falsy since we're going in reverse.
+          break;
+        }
+
+        delete state._closedWindows[i]._shouldRestore;
+        state.windows.unshift(state._closedWindows.pop());
       }
-
-      delete state._closedWindows[i]._shouldRestore;
-      state.windows.unshift(state._closedWindows.pop());
     }
-#endif
 
     stopWatchFinish("COLLECT_DATA_MS", "COLLECT_DATA_LONGEST_OP_MS");
     return this._writeState(state);
diff --git a/browser/components/sessionstore/SessionStore.jsm b/browser/components/sessionstore/SessionStore.jsm
index 5a5a52b37e..d1cc081678 100644
--- a/browser/components/sessionstore/SessionStore.jsm
+++ b/browser/components/sessionstore/SessionStore.jsm
@@ -131,29 +131,15 @@ XPCOMUtils.defineLazyModuleGetter(this, "console",
   "resource://gre/modules/devtools/Console.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "RecentWindow",
   "resource:///modules/RecentWindow.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "AppConstants",
+  "resource://gre/modules/AppConstants.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "GlobalState",
   "resource:///modules/sessionstore/GlobalState.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "PrivacyFilter",
   "resource:///modules/sessionstore/PrivacyFilter.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "RunState",
   "resource:///modules/sessionstore/RunState.jsm");
-
-#ifdef MOZ_DEVTOOLS
-
-Object.defineProperty(this, "HUDService", {
-  get: function HUDService_getter() {
-    let devtools = Cu.import("resource://gre/modules/devtools/Loader.jsm", {}).devtools;
-    return devtools.require("devtools/webconsole/hudservice").HUDService;
-  },
-  configurable: true,
-  enumerable: true
-});
-#endif  
-  
-XPCOMUtils.defineLazyModuleGetter(this, "DocumentUtils",
-  "resource:///modules/sessionstore/DocumentUtils.jsm");
-XPCOMUtils.defineLazyModuleGetter(this, "PrivacyLevel",
-  "resource:///modules/sessionstore/PrivacyLevel.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "ScratchpadManager",
   "resource://gre/modules/devtools/scratchpad-manager.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "SessionSaver",
@@ -162,8 +148,8 @@ XPCOMUtils.defineLazyModuleGetter(this, "SessionCookies",
   "resource:///modules/sessionstore/SessionCookies.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "SessionFile",
   "resource:///modules/sessionstore/SessionFile.jsm");
-XPCOMUtils.defineLazyModuleGetter(this, "SessionHistory",
-  "resource:///modules/sessionstore/SessionHistory.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "TabAttributes",
+  "resource:///modules/sessionstore/TabAttributes.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "TabState",
   "resource:///modules/sessionstore/TabState.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "TabStateCache",
@@ -368,6 +354,9 @@ let SessionStoreInternal = {
   // states for all currently opened windows
   _windows: {},
 
+  // counter for creating unique window IDs
+  _nextWindowID: 0,
+
   // states for all recently closed windows
   _closedWindows: [],
 
@@ -498,10 +487,8 @@ let SessionStoreInternal = {
             }
           }
 
-          // Load the session start time from the previous state
-          this._sessionStartTime = state.session &&
-                                   state.session.startTime ||
-                                   this._sessionStartTime;
+          // Update the session start time using the restored session state.
+          this._updateSessionStartTime(state);
 
           // make sure that at least the first window doesn't have anything hidden
           delete state.windows[0].hidden;
@@ -772,6 +759,15 @@ let SessionStoreInternal = {
     this._clearRestoringWindows();
   },
 
+  /**
+   * Generate a unique window identifier
+   * @return string
+   *         A unique string to identify a window
+   */
+  _generateWindowID: function ssi_generateWindowID() {
+    return "window" + (this._nextWindowID++);
+  },
+
   /**
    * If it's the first window load since app start...
    * - determine if we're reloading after a crash or a forced-restart
@@ -792,8 +788,9 @@ let SessionStoreInternal = {
     if (RunState.isQuitting)
       return;
 
-    // assign it a unique identifier (timestamp)
-    aWindow.__SSi = "window" + Date.now();
+    // Assign the window a unique identifier we can use to reference
+    // internal data about the window.
+    aWindow.__SSi = this._generateWindowID();
 
     let mm = aWindow.getGroupMessageManager("browsers");
     MESSAGES.forEach(msg => {
@@ -889,9 +886,7 @@ let SessionStoreInternal = {
 
       if (closedWindowState) {
         let newWindowState;
-#ifndef XP_MACOSX
-        if (!this._doResumeSession()) {
-#endif
+        if (AppConstants.platform == "macosx" || !this._doResumeSession()) {
           // We want to split the window up into pinned tabs and unpinned tabs.
           // Pinned tabs should be restored. If there are any remaining tabs,
           // they should be added back to _closedWindows.
@@ -915,7 +910,6 @@ let SessionStoreInternal = {
             delete normalTabsState.windows[0].__lastSessionWindowID;
             this._closedWindows[closedWindowIndex] = normalTabsState.windows[0];
           }
-#ifndef XP_MACOSX
         }
         else {
           // If we're just restoring the window, make sure it gets removed from
@@ -924,7 +918,7 @@ let SessionStoreInternal = {
           newWindowState = closedWindowState;
           delete newWindowState.hidden;
         }
-#endif
+
         if (newWindowState) {
           // Ensure that the window state isn't hidden
           this._restoreCount = 1;
@@ -1031,8 +1025,10 @@ let SessionStoreInternal = {
     // this window was about to be restored - conserve its original data, if any
     let isFullyLoaded = this._isWindowLoaded(aWindow);
     if (!isFullyLoaded) {
-      if (!aWindow.__SSi)
-        aWindow.__SSi = "window" + Date.now();
+      if (!aWindow.__SSi) {
+        aWindow.__SSi = this._generateWindowID();
+      }
+
       this._windows[aWindow.__SSi] = this._statesToRestore[aWindow.__SS_restoreID];
       delete this._statesToRestore[aWindow.__SS_restoreID];
       delete aWindow.__SS_restoreID;
@@ -1077,11 +1073,11 @@ let SessionStoreInternal = {
         SessionCookies.update([winData]);
       }
 
-#ifndef XP_MACOSX
-      // Until we decide otherwise elsewhere, this window is part of a series
-      // of closing windows to quit.
-      winData._shouldRestore = true;
-#endif
+      if (AppConstants.platform != "macosx") {
+        // Until we decide otherwise elsewhere, this window is part of a series
+        // of closing windows to quit.
+        winData._shouldRestore = true;
+      }
 
       // Store the window's close date to figure out when each individual tab
       // was closed. This timestamp should allow re-arranging data based on how
@@ -1994,24 +1990,16 @@ let SessionStoreInternal = {
       this._capClosedWindows();
     }
 
-#ifdef MOZ_DEVTOOLS
-    // Scratchpad
     if (lastSessionState.scratchpads) {
       ScratchpadManager.restoreSession(lastSessionState.scratchpads);
     }
 
-    // The Browser Console
-    if (lastSessionState.browserConsole) {
-      HUDService.restoreBrowserConsoleSession();
-    }
-#endif
-
     // Set data that persists between sessions
     this._recentCrashes = lastSessionState.session &&
                           lastSessionState.session.recentCrashes || 0;
-    this._sessionStartTime = lastSessionState.session &&
-                             lastSessionState.session.startTime ||
-                             this._sessionStartTime;
+
+    // Update the session start time using the restored session state.
+    this._updateSessionStartTime(lastSessionState);
 
     LastSession.clear();
   },
@@ -2194,21 +2182,21 @@ let SessionStoreInternal = {
     // shallow copy this._closedWindows to preserve current state
     let lastClosedWindowsCopy = this._closedWindows.slice();
 
-#ifndef XP_MACOSX
-    // If no non-popup browser window remains open, return the state of the last
-    // closed window(s). We only want to do this when we're actually "ending"
-    // the session.
-    //XXXzpao We should do this for _restoreLastWindow == true, but that has
-    //        its own check for popups. c.f. bug 597619
-    if (nonPopupCount == 0 && lastClosedWindowsCopy.length > 0 &&
-        RunState.isQuitting) {
-      // prepend the last non-popup browser window, so that if the user loads more tabs
-      // at startup we don't accidentally add them to a popup window
-      do {
-        total.unshift(lastClosedWindowsCopy.shift())
-      } while (total[0].isPopup && lastClosedWindowsCopy.length > 0)
+    if (AppConstants.platform != "macosx") {
+      // If no non-popup browser window remains open, return the state of the last
+      // closed window(s). We only want to do this when we're actually "ending"
+      // the session.
+      //XXXzpao We should do this for _restoreLastWindow == true, but that has
+      //        its own check for popups. c.f. bug 597619
+      if (nonPopupCount == 0 && lastClosedWindowsCopy.length > 0 &&
+          RunState.isQuitting) {
+        // prepend the last non-popup browser window, so that if the user loads more tabs
+        // at startup we don't accidentally add them to a popup window
+        do {
+          total.unshift(lastClosedWindowsCopy.shift())
+        } while (total[0].isPopup && lastClosedWindowsCopy.length > 0)
+      }
     }
-#endif
 
     if (activeWindow) {
       this.activeWindowSSiCache = activeWindow.__SSi || "";
@@ -2494,17 +2482,10 @@ let SessionStoreInternal = {
         (overwriteTabs ? (parseInt(winData.selected || "1")) : 0));
     }
 
-#ifdef MOZ_DEVTOOLS
     if (aState.scratchpads) {
       ScratchpadManager.restoreSession(aState.scratchpads);
     }
 
-    // The Browser Console
-    if (aState.browserConsole) {
-      HUDService.restoreBrowserConsoleSession();
-    }
-
-#endif
     // set smoothScroll back to the original value
     tabstrip.smoothScroll = smoothScroll;
 
@@ -2907,6 +2888,20 @@ let SessionStoreInternal = {
 
   /* ........ Auxiliary Functions .............. */
 
+  /**
+   * Update the session start time and send a telemetry measurement
+   * for the number of days elapsed since the session was started.
+   *
+   * @param state
+   *        The session state.
+   */
+  _updateSessionStartTime: function ssi_updateSessionStartTime(state) {
+    // Attempt to load the session start time from the session state
+    if (state.session && state.session.startTime) {
+      this._sessionStartTime = state.session.startTime;
+    }
+  },
+
   /**
    * call a callback for all currently opened browser windows
    * (might miss the most recent one)
@@ -3396,15 +3391,15 @@ let SessionStoreInternal = {
     if (this._closedWindows.length <= this._max_windows_undo)
       return;
     let spliceTo = this._max_windows_undo;
-#ifndef XP_MACOSX
-    let normalWindowIndex = 0;
-    // try to find a non-popup window in this._closedWindows
-    while (normalWindowIndex < this._closedWindows.length &&
-           !!this._closedWindows[normalWindowIndex].isPopup)
-      normalWindowIndex++;
-    if (normalWindowIndex >= this._max_windows_undo)
-      spliceTo = normalWindowIndex + 1;
-#endif
+    if (AppConstants.platform != "macosx") {
+      let normalWindowIndex = 0;
+      // try to find a non-popup window in this._closedWindows
+      while (normalWindowIndex < this._closedWindows.length &&
+             !!this._closedWindows[normalWindowIndex].isPopup)
+        normalWindowIndex++;
+      if (normalWindowIndex >= this._max_windows_undo)
+        spliceTo = normalWindowIndex + 1;
+    }
     this._closedWindows.splice(spliceTo, this._closedWindows.length);
   },
 
@@ -3733,72 +3728,6 @@ let DirtyWindows = {
   }
 };
 
-// A map storing the number of tabs last closed per windoow. This only
-// stores the most recent tab-close operation, and is used to undo
-// batch tab-closing operations.
-let NumberOfTabsClosedLastPerWindow = new WeakMap();
-
-// A set of tab attributes to persist. We will read a given list of tab
-// attributes when collecting tab data and will re-set those attributes when
-// the given tab data is restored to a new tab.
-let TabAttributes = {
-  _attrs: new Set(),
-
-  // We never want to directly read or write those attributes.
-  // 'image' should not be accessed directly but handled by using the
-  //         gBrowser.getIcon()/setIcon() methods.
-  // 'pending' is used internal by sessionstore and managed accordingly.
-  _skipAttrs: new Set(["image", "pending"]),
-
-  persist: function (name) {
-    if (this._attrs.has(name) || this._skipAttrs.has(name)) {
-      return false;
-    }
-
-    this._attrs.add(name);
-    return true;
-  },
-
-  get: function (tab) {
-    let data = {};
-
-    for (let name of this._attrs) {
-      if (tab.hasAttribute(name)) {
-        data[name] = tab.getAttribute(name);
-      }
-    }
-
-    return data;
-  },
-
-  set: function (tab, data = {}) {
-    // Clear attributes.
-    for (let name of this._attrs) {
-      tab.removeAttribute(name);
-    }
-
-    // Set attributes.
-    for (let name in data) {
-      tab.setAttribute(name, data[name]);
-    }
-  }
-};
-
-
-// see nsPrivateBrowsingService.js
-String.prototype.hasRootDomain = function hasRootDomain(aDomain) {
-  let index = this.indexOf(aDomain);
-  if (index == -1)
-    return false;
-
-  if (this == aDomain)
-    return true;
-
-  let prevChar = this[index - 1];
-  return (index == (this.length - aDomain.length)) &&
-         (prevChar == "." || prevChar == "/");
-};
-
 function TabData(obj = null) {
   if (obj) {
     if (obj instanceof TabData) {
diff --git a/browser/components/sessionstore/content/aboutSessionRestore.js b/browser/components/sessionstore/content/aboutSessionRestore.js
index 3911b77484..e51fde5a6a 100644
--- a/browser/components/sessionstore/content/aboutSessionRestore.js
+++ b/browser/components/sessionstore/content/aboutSessionRestore.js
@@ -2,8 +2,12 @@
  * 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/. */
 
-const Cc = Components.classes;
-const Ci = Components.interfaces;
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "AppConstants",
+  "resource://gre/modules/AppConstants.jsm");
 
 var gStateObject;
 var gTreeData;
@@ -11,6 +15,14 @@ var gTreeData;
 // Page initialization
 
 window.onload = function() {
+  // pages used by this script may have a link that needs to be updated to
+  // the in-product link.
+  let anchor = document.getElementById("linkMoreTroubleshooting");
+  if (anchor) {
+    let baseURL = Services.urlFormatter.formatURLPref("app.support.baseURL");
+    anchor.setAttribute("href", baseURL + "troubleshooting");
+  }
+
   // the crashed session state is kept inside a textbox so that SessionStore picks it up
   // (for when the tab is closed or the session crashes right again)
   var sessionData = document.getElementById("sessionData");
@@ -70,6 +82,14 @@ function initTreeView() {
 function restoreSession() {
   document.getElementById("errorTryAgain").disabled = true;
 
+  if (!gTreeData.some(aItem => aItem.checked)) {
+    // This should only be possible when we have no "cancel" button, and thus
+    // the "Restore session" button always remains enabled.  In that case and
+    // when nothing is selected, we just want a new session.
+    startNewSession();
+    return;
+  }
+
   // remove all unselected tabs from the state before restoring it
   var ix = gStateObject.windows.length - 1;
   for (var t = gTreeData.length - 1; t >= 0; t--) {
@@ -131,11 +151,9 @@ function onListClick(aEvent) {
   if (cell.col) {
     // Restore this specific tab in the same window for middle/double/accel clicking
     // on a tab's title.
-#ifdef XP_MACOSX
-    let accelKey = aEvent.metaKey;
-#else
-    let accelKey = aEvent.ctrlKey;
-#endif
+    let accelKey = AppConstants.platform == "macosx" ?
+                   aEvent.metaKey :
+                   aEvent.ctrlKey;
     if ((aEvent.button == 1 || aEvent.button == 0 && aEvent.detail == 2 || accelKey) &&
         cell.col.id == "title" &&
         !treeView.isContainer(cell.row)) {
@@ -158,14 +176,6 @@ function onListKeyDown(aEvent) {
     if (aEvent.ctrlKey && !treeView.isContainer(ix))
       restoreSingleTab(ix, aEvent.shiftKey);
     break;
-  case KeyEvent.DOM_VK_UP:
-  case KeyEvent.DOM_VK_DOWN:
-  case KeyEvent.DOM_VK_PAGE_UP:
-  case KeyEvent.DOM_VK_PAGE_DOWN:
-  case KeyEvent.DOM_VK_HOME:
-  case KeyEvent.DOM_VK_END:
-    aEvent.preventDefault(); // else the page scrolls unwantedly
-    break;
   }
 }
 
@@ -198,7 +208,10 @@ function toggleRowChecked(aIx) {
     treeView.treeBox.invalidateRow(gTreeData.indexOf(item.parent));
   }
 
-  document.getElementById("errorTryAgain").disabled = !gTreeData.some(isChecked);
+  // we only disable the button when there's no cancel button.
+  if (document.getElementById("errorCancel")) {
+    document.getElementById("errorTryAgain").disabled = !gTreeData.some(isChecked);
+  }
 }
 
 function restoreSingleTab(aIx, aShifted) {
diff --git a/browser/components/sessionstore/jar.mn b/browser/components/sessionstore/jar.mn
index 529692e7eb..7e5bc07dc6 100644
--- a/browser/components/sessionstore/jar.mn
+++ b/browser/components/sessionstore/jar.mn
@@ -4,5 +4,5 @@
 
 browser.jar:
 *   content/browser/aboutSessionRestore.xhtml             (content/aboutSessionRestore.xhtml)
-*   content/browser/aboutSessionRestore.js                (content/aboutSessionRestore.js)
+    content/browser/aboutSessionRestore.js                (content/aboutSessionRestore.js)
     content/browser/content-sessionStore.js               (content/content-sessionStore.js)
diff --git a/browser/components/sessionstore/moz.build b/browser/components/sessionstore/moz.build
index d9e1c6ada8..6170b9fd21 100644
--- a/browser/components/sessionstore/moz.build
+++ b/browser/components/sessionstore/moz.build
@@ -34,7 +34,9 @@ EXTRA_JS_MODULES.sessionstore = [
     'SessionFile.jsm',
     'SessionHistory.jsm',
     'SessionMigration.jsm',
+    'SessionSaver.jsm',
     'SessionStorage.jsm',
+    'SessionStore.jsm',
     'SessionWorker.js',
     'SessionWorker.jsm',
     'TabAttributes.jsm',
@@ -45,7 +47,3 @@ EXTRA_JS_MODULES.sessionstore = [
     'XPathGenerator.jsm',
 ]
 
-EXTRA_PP_JS_MODULES.sessionstore += [
-    'SessionSaver.jsm',
-    'SessionStore.jsm',
-]
diff --git a/browser/locales/en-US/chrome/browser/aboutSessionRestore.dtd b/browser/locales/en-US/chrome/browser/aboutSessionRestore.dtd
index 51213d6567..4983a7aff6 100644
--- a/browser/locales/en-US/chrome/browser/aboutSessionRestore.dtd
+++ b/browser/locales/en-US/chrome/browser/aboutSessionRestore.dtd
@@ -23,12 +23,28 @@
 <!ENTITY restorepage.windowLabel    "Window &#37;S">
 
 
-<!-- LOCALIZATION NOTE: The following 'welcomeback' strings are for about:welcomeback,
+<!-- LOCALIZATION NOTE: The following 'welcomeback2' strings are for about:welcomeback,
      not for about:sessionstore -->
-<!ENTITY welcomeback.tabtitle       "Welcome Back!">
 
-<!-- LOCALIZATION NOTE: The title is intended to be welcoming and congratulatory,
-     expressing joy that the user has successfully migrated their stuff and hope
-     that now they have a better experience.  -->
-<!ENTITY welcomeback.pageTitle      "Welcome Back!">
-<!ENTITY welcomeback.pageInfo       "&brandShortName; successfully reset your profile. Below is a list of windows and tabs you had open; you can restore them or start with a clean slate.">
+<!ENTITY welcomeback2.restoreButton  "Let's go!">
+<!ENTITY welcomeback2.restoreButton.access "L">
+
+<!ENTITY welcomeback2.tabtitle      "Success!">
+
+<!ENTITY welcomeback2.pageTitle     "Success!">
+<!ENTITY welcomeback2.pageInfo1     "&brandShortName; is ready to go.">
+
+<!ENTITY welcomeback2.label.restoreAll  "Restore all Windows and Tabs">
+<!ENTITY welcomeback2.label.restoreSome "Restore only the ones you want">
+
+
+<!-- LOCALIZATION NOTE (welcomeback2.beforelink.pageInfo2,
+welcomeback2.afterlink.pageInfo2): these two string are used respectively
+before and after the the "learn more" link (welcomeback2.link.pageInfo2).
+Localizers can use one of them, or both, to better adapt this sentence to
+their language.
+-->
+<!ENTITY welcomeback2.beforelink.pageInfo2  "Your add-ons and customizations have been removed and your browser settings have been restored to their defaults. If this didn't fix your issue, ">
+<!ENTITY welcomeback2.afterlink.pageInfo2   "">
+
+<!ENTITY welcomeback2.link.pageInfo2        "learn more about what you can do.">
diff --git a/browser/locales/en-US/chrome/browser/safeMode.dtd b/browser/locales/en-US/chrome/browser/safeMode.dtd
index 79d3ca87c6..ab23731c16 100644
--- a/browser/locales/en-US/chrome/browser/safeMode.dtd
+++ b/browser/locales/en-US/chrome/browser/safeMode.dtd
@@ -3,25 +3,15 @@
    - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
 
 <!ENTITY safeModeDialog.title         "&brandShortName; Safe Mode">
-<!ENTITY window.width                 "37em">
+<!ENTITY window.maxWidth              "400">
 
-<!ENTITY safeModeDescription.label    "&brandShortName; is now running in Safe Mode, which temporarily disables your custom settings, themes, and extensions.">
-<!ENTITY safeModeDescription2.label   "You can make some or all of these changes permanent:">
+<!ENTITY startSafeMode.label          "Start in Safe Mode">
+<!ENTITY refreshProfile.label         "Refresh &brandShortName;">
 
-<!ENTITY disableAddons.label          "Disable all add-ons">
-<!ENTITY disableAddons.accesskey      "D">
+<!ENTITY safeModeDescription3.label   "Safe Mode is a special mode of &brandShortName; that can be used to troubleshoot issues.">
+<!ENTITY safeModeDescription4.label   "Your add-ons and custom settings will be temporarily disabled.">
 
-<!ENTITY resetToolbars.label          "Reset toolbars and controls">
-<!ENTITY resetToolbars.accesskey      "R">
+<!ENTITY refreshProfileInstead.label  "You can also skip troubleshooting and try refreshing &brandShortName;.">
 
-<!ENTITY deleteBookmarks.label        "Delete all bookmarks except for backups">
-<!ENTITY deleteBookmarks.accesskey    "b">
-
-<!ENTITY resetUserPrefs.label         "Reset all user preferences to &brandShortName; defaults">
-<!ENTITY resetUserPrefs.accesskey     "p">
-
-<!ENTITY restoreSearch.label          "Restore default search engines">
-<!ENTITY restoreSearch.accesskey      "s">
-
-<!ENTITY changeAndRestartButton.label "Make Changes and Restart">
-<!ENTITY continueButton.label         "Continue in Safe Mode">
+<!-- LOCALIZATION NOTE (autoSafeModeDescription3.label): Shown on the safe mode dialog after multiple startup crashes. See also chrome/global/resetProfile.dtd -->
+<!ENTITY autoSafeModeDescription3.label "&brandShortName; closed unexpectedly while starting. This might be caused by add-ons or other problems. You can try to resolve the problem by troubleshooting in Safe Mode.">
diff --git a/dom/canvas/DocumentRendererChild.cpp b/dom/canvas/DocumentRendererChild.cpp
index d81d00d052..e176578bab 100644
--- a/dom/canvas/DocumentRendererChild.cpp
+++ b/dom/canvas/DocumentRendererChild.cpp
@@ -80,6 +80,10 @@ DocumentRendererChild::RenderDocument(nsIDOMWindow *window,
                                          IntSize(renderSize.width, renderSize.height),
                                          4 * renderSize.width,
                                          SurfaceFormat::B8G8R8A8);
+    if (!dt) {
+        gfxWarning() << "DocumentRendererChild::RenderDocument failed to Factory::CreateDrawTargetForData";
+        return false;
+    }
     nsRefPtr<gfxContext> ctx = new gfxContext(dt);
     ctx->SetMatrix(mozilla::gfx::ThebesMatrix(transform));
 
diff --git a/gfx/2d/DrawTargetTiled.h b/gfx/2d/DrawTargetTiled.h
index b709aee694..aa9af05f16 100644
--- a/gfx/2d/DrawTargetTiled.h
+++ b/gfx/2d/DrawTargetTiled.h
@@ -187,6 +187,11 @@ public:
         Factory::CreateDrawTargetForData(BackendType::CAIRO, mappedSurf.mData,
         GetSize(), mappedSurf.mStride, GetFormat());
 
+      if (!dt) {
+        gfxWarning() << "DrawTargetTiled::GetDataSurface failed in CreateDrawTargetForData";
+        surf->Unmap();
+        return nullptr;
+      }
       for (size_t i = 0; i < mSnapshots.size(); i++) {
         RefPtr<DataSourceSurface> dataSurf = mSnapshots[i]->GetDataSurface();
         dt->CopySurface(dataSurf, IntRect(IntPoint(0, 0), mSnapshots[i]->GetSize()), mOrigins[i]);
diff --git a/gfx/2d/FilterNodeSoftware.cpp b/gfx/2d/FilterNodeSoftware.cpp
index 79363a227b..f67e149a68 100644
--- a/gfx/2d/FilterNodeSoftware.cpp
+++ b/gfx/2d/FilterNodeSoftware.cpp
@@ -994,6 +994,11 @@ FilterNodeBlendSoftware::Render(const IntRect& aRect)
 	                                     target->Stride(),
 	                                     target->GetFormat());
 
+  if (!dt) {
+    gfxWarning() << "FilterNodeBlendSoftware::Render failed in CreateDrawTargetForData";
+    return nullptr;
+  }
+
   Rect r(0, 0, size.width, size.height);
   dt->DrawSurface(input2, r, r, DrawSurfaceOptions(), DrawOptions(1.0f, ToBlendOp(mBlendMode)));
   dt->Flush();
@@ -1102,6 +1107,7 @@ FilterNodeTransformSoftware::Render(const IntRect& aRect)
                                      mapping.mStride,
                                      surf->GetFormat());
   if (!dt) {
+    gfxWarning() << "FilterNodeTransformSoftware::Render failed in CreateDrawTargetForData";
     return nullptr;
   }
 
diff --git a/gfx/layers/client/ImageClient.cpp b/gfx/layers/client/ImageClient.cpp
index dee2154533..b500f9f6cf 100644
--- a/gfx/layers/client/ImageClient.cpp
+++ b/gfx/layers/client/ImageClient.cpp
@@ -229,6 +229,10 @@ ImageClientSingle::UpdateImage(ImageContainer* aContainer, uint32_t aContentFlag
       {
         // We must not keep a reference to the DrawTarget after it has been unlocked.
         DrawTarget* dt = texture->BorrowDrawTarget();
+        if (!dt) {
+          gfxWarning() << "ImageClientSingle::UpdateImage failed in BorrowDrawTarget";
+          return false;
+        }
         MOZ_ASSERT(surface.get());
         dt->CopySurface(surface, IntRect(IntPoint(), surface->GetSize()), IntPoint());
       }
diff --git a/gfx/layers/client/TextureClient.cpp b/gfx/layers/client/TextureClient.cpp
index cfed40c603..65e49d6ed4 100644
--- a/gfx/layers/client/TextureClient.cpp
+++ b/gfx/layers/client/TextureClient.cpp
@@ -544,7 +544,17 @@ bool TextureClient::CopyToTextureClient(TextureClient* aTarget,
   }
 
   RefPtr<DrawTarget> destinationTarget = aTarget->BorrowDrawTarget();
+  if (!destinationTarget) {
+      gfxWarning() << "TextureClient::CopyToTextureClient (dest) failed in BorrowDrawTarget";
+    return false;
+  }
+
   RefPtr<DrawTarget> sourceTarget = BorrowDrawTarget();
+  if (!sourceTarget) {
+    gfxWarning() << "TextureClient::CopyToTextureClient (src) failed in BorrowDrawTarget";
+    return false;
+  }
+
   RefPtr<gfx::SourceSurface> source = sourceTarget->Snapshot();
   destinationTarget->CopySurface(source,
                                  aRect ? *aRect : gfx::IntRect(gfx::IntPoint(0, 0), GetSize()),
diff --git a/gfx/layers/d3d11/TextureD3D11.cpp b/gfx/layers/d3d11/TextureD3D11.cpp
index 4bb06ee4e9..a9aaad566a 100644
--- a/gfx/layers/d3d11/TextureD3D11.cpp
+++ b/gfx/layers/d3d11/TextureD3D11.cpp
@@ -291,11 +291,19 @@ TextureClientD3D11::Lock(OpenMode aMode)
 
   if (mNeedsClear) {
     mDrawTarget = BorrowDrawTarget();
+    if (!mDrawTarget) {
+        Unlock();
+        return false;
+    }
     mDrawTarget->ClearRect(Rect(0, 0, GetSize().width, GetSize().height));
     mNeedsClear = false;
   }
   if (mNeedsClearWhite) {
     mDrawTarget = BorrowDrawTarget();
+    if (!mDrawTarget) {
+        Unlock();
+        return false;
+    }
     mDrawTarget->FillRect(Rect(0, 0, GetSize().width, GetSize().height), ColorPattern(Color(1.0, 1.0, 1.0, 1.0)));
     mNeedsClearWhite = false;
   }
diff --git a/gfx/layers/d3d9/TextureD3D9.cpp b/gfx/layers/d3d9/TextureD3D9.cpp
index d800133752..b917669b8c 100644
--- a/gfx/layers/d3d9/TextureD3D9.cpp
+++ b/gfx/layers/d3d9/TextureD3D9.cpp
@@ -295,17 +295,19 @@ TextureSourceD3D9::SurfaceToTexture(DeviceManagerD3D9* aDeviceManager,
                                        reinterpret_cast<unsigned char*>(lockedRect.pBits),
                                        aSize, lockedRect.Pitch,
                                        gfxPlatform::GetPlatform()->Optimal2DFormatForContent(aSurface->GetContentType()));
-    NativeSurface nativeSurf;
-    nativeSurf.mSize = aSize;
-    nativeSurf.mType = NativeSurfaceType::CAIRO_SURFACE;
-    // We don't know that this is actually the right format, but it's the best
-    // we can get for the content type. In practice this probably always works.
-    nativeSurf.mFormat = dt->GetFormat();
-    nativeSurf.mSurface = aSurface->CairoSurface();
 
-    RefPtr<SourceSurface> surf = dt->CreateSourceSurfaceFromNativeSurface(nativeSurf);
+    if (dt) {
+        NativeSurface nativeSurf;
+        nativeSurf.mSize = aSize;
+        nativeSurf.mType = NativeSurfaceType::CAIRO_SURFACE;
+        // We don't know that this is actually the right format, but it's the best
+        // we can get for the content type. In practice this probably always works.
+        nativeSurf.mFormat = dt->GetFormat();
+        nativeSurf.mSurface = aSurface->CairoSurface();
 
-    dt->CopySurface(surf, IntRect(IntPoint(), aSize), IntPoint());
+        RefPtr<SourceSurface> surf = dt->CreateSourceSurfaceFromNativeSurface(nativeSurf);
+        dt->CopySurface(surf, IntRect(IntPoint(), aSize), IntPoint());
+    }
   }
 
   FinishTextures(aDeviceManager, texture, surface);
@@ -623,11 +625,19 @@ CairoTextureClientD3D9::Lock(OpenMode aMode)
 
   if (mNeedsClear) {
     mDrawTarget = BorrowDrawTarget();
+    if (!mDrawTarget) {
+      Unlock();
+      return false;
+    }
     mDrawTarget->ClearRect(Rect(0, 0, GetSize().width, GetSize().height));
     mNeedsClear = false;
   }
   if (mNeedsClearWhite) {
     mDrawTarget = BorrowDrawTarget();
+    if (!mDrawTarget) {
+      Unlock();
+      return false;
+    }
     mDrawTarget->FillRect(Rect(0, 0, GetSize().width, GetSize().height), ColorPattern(Color(1.0, 1.0, 1.0, 1.0)));
     mNeedsClearWhite = false;
   }
diff --git a/gfx/layers/opengl/CompositorOGL.cpp b/gfx/layers/opengl/CompositorOGL.cpp
index 915e31748e..7c9bfbd1c1 100644
--- a/gfx/layers/opengl/CompositorOGL.cpp
+++ b/gfx/layers/opengl/CompositorOGL.cpp
@@ -1228,9 +1228,10 @@ CompositorOGL::EndFrame()
       mWidget->GetBounds(rect);
     }
     RefPtr<DrawTarget> target = gfxPlatform::GetPlatform()->CreateOffscreenContentDrawTarget(IntSize(rect.width, rect.height), SurfaceFormat::B8G8R8A8);
-    CopyToTarget(target, nsIntPoint(), Matrix());
-
-    WriteSnapshotToDumpFile(this, target);
+    if (target) {
+      CopyToTarget(target, nsIntPoint(), Matrix());
+      WriteSnapshotToDumpFile(this, target);
+    }
   }
 #endif
 
@@ -1342,6 +1343,7 @@ CompositorOGL::SetDestinationSurfaceSize(const gfx::IntSize& aSize)
 void
 CompositorOGL::CopyToTarget(DrawTarget* aTarget, const nsIntPoint& aTopLeft, const gfx::Matrix& aTransform)
 {
+  MOZ_ASSERT(aTarget);
   IntRect rect;
   if (mUseExternalSurfaceSize) {
     rect = IntRect(0, 0, mSurfaceSize.width, mSurfaceSize.height);
diff --git a/gfx/thebes/gfxPlatform.cpp b/gfx/thebes/gfxPlatform.cpp
index 111e97690e..1eb45c785a 100644
--- a/gfx/thebes/gfxPlatform.cpp
+++ b/gfx/thebes/gfxPlatform.cpp
@@ -729,6 +729,10 @@ gfxPlatform::CreateDrawTargetForSurface(gfxASurface *aSurface, const IntSize& aS
 {
   SurfaceFormat format = Optimal2DFormatForContent(aSurface->GetContentType());
   RefPtr<DrawTarget> drawTarget = Factory::CreateDrawTargetForCairoSurface(aSurface->CairoSurface(), aSize, &format);
+  if (!drawTarget) {
+    gfxWarning() << "gfxPlatform::CreateDrawTargetForSurface failed in CreateDrawTargetForCairoSurface";
+    return nullptr;
+  }
   aSurface->SetData(&kDrawTarget, drawTarget, nullptr);
   return drawTarget.forget();
 }
@@ -912,6 +916,10 @@ gfxPlatform::GetSourceSurfaceForSurface(DrawTarget *aTarget, gfxASurface *aSurfa
     surf.mSize = ToIntSize(aSurface->GetSize());
     RefPtr<DrawTarget> drawTarget =
       Factory::CreateDrawTarget(BackendType::CAIRO, IntSize(1, 1), format);
+    if (!drawTarget) {
+      gfxWarning() << "gfxPlatform::GetSourceSurfaceForSurface failed in CreateDrawTarget";
+      return nullptr;
+    }
     srcBuffer = drawTarget->CreateSourceSurfaceFromNativeSurface(surf);
     if (srcBuffer) {
       srcBuffer = aTarget->OptimizeSourceSurface(srcBuffer);
diff --git a/gfx/thebes/gfxUtils.cpp b/gfx/thebes/gfxUtils.cpp
index 2d14bc8ec4..f1d9373b28 100644
--- a/gfx/thebes/gfxUtils.cpp
+++ b/gfx/thebes/gfxUtils.cpp
@@ -14,6 +14,7 @@
 #include "mozilla/Base64.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/gfx/DataSurfaceHelpers.h"
+#include "mozilla/gfx/Logging.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/Vector.h"
@@ -1038,6 +1039,11 @@ gfxUtils::CopySurfaceToDataSourceSurfaceWithFormat(SourceSurface* aSurface,
     // GPU.
     RefPtr<DrawTarget> dt = gfxPlatform::GetPlatform()->
       CreateOffscreenContentDrawTarget(aSurface->GetSize(), aFormat);
+    if (!dt) {
+      gfxWarning() << "gfxUtils::CopySurfaceToDataSourceSurfaceWithFormat failed in CreateOffscreenContentDrawTarget";
+      return nullptr;
+    }
+
     // Using DrawSurface() here rather than CopySurface() because CopySurface
     // is optimized for memcpy and therefore isn't good for format conversion.
     // Using OP_OVER since in our case it's equivalent to OP_SOURCE and
diff --git a/image/DynamicImage.cpp b/image/DynamicImage.cpp
index a967762ca5..728deabc30 100644
--- a/image/DynamicImage.cpp
+++ b/image/DynamicImage.cpp
@@ -184,6 +184,10 @@ DynamicImage::GetFrame(uint32_t aWhichFrame,
   RefPtr<DrawTarget> dt = gfxPlatform::GetPlatform()->
     CreateOffscreenContentDrawTarget(IntSize(size.width, size.height),
                                      SurfaceFormat::B8G8R8A8);
+  if (!dt) {
+    gfxWarning() << "DynamicImage::GetFrame failed in CreateOffscreenContentDrawTarget";
+    return nullptr;
+  }
   nsRefPtr<gfxContext> context = new gfxContext(dt);
 
   auto result = Draw(context, size, ImageRegion::Create(size),
diff --git a/image/RasterImage.cpp b/image/RasterImage.cpp
index 1ca1f6bb49..7cb11f044a 100644
--- a/image/RasterImage.cpp
+++ b/image/RasterImage.cpp
@@ -710,6 +710,10 @@ RasterImage::CopyFrame(uint32_t aWhichFrame, uint32_t aFlags)
                                      size,
                                      mapping.mStride,
                                      SurfaceFormat::B8G8R8A8);
+  if (!target) {
+    gfxWarning() << "RasterImage::CopyFrame failed in CreateDrawTargetForData";
+    return nullptr;
+  }
 
   nsIntRect intFrameRect = frameRef->GetRect();
   Rect rect(intFrameRect.x, intFrameRect.y,
diff --git a/image/imgFrame.cpp b/image/imgFrame.cpp
index c0ec6f22be..c2215b4316 100644
--- a/image/imgFrame.cpp
+++ b/image/imgFrame.cpp
@@ -484,6 +484,10 @@ nsresult imgFrame::Optimize()
                                        mapping.mStride,
                                        optFormat);
 
+    if (!target) {
+      gfxWarning() << "imgFrame::Optimize failed in CreateDrawTargetForData";
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
     Rect rect(0, 0, mSize.width, mSize.height);
     target->DrawSurface(mImageSurface, rect, rect);
     target->Flush();
@@ -891,6 +895,10 @@ imgFrame::Deoptimize()
                                          mSize,
                                          mapping.mStride,
                                          format);
+      if (!target) {
+        gfxWarning() << "imgFrame::Deoptimize failed in CreateDrawTargetForData";
+        return NS_ERROR_OUT_OF_MEMORY;
+      }
 
       Rect rect(0, 0, mSize.width, mSize.height);
       if (mSinglePixel)
diff --git a/image/imgTools.cpp b/image/imgTools.cpp
index b81ac32deb..c128df3f3f 100644
--- a/image/imgTools.cpp
+++ b/image/imgTools.cpp
@@ -221,6 +221,11 @@ NS_IMETHODIMP imgTools::EncodeScaledImage(imgIContainer *aContainer,
                                      dataSurface->GetSize(),
                                      map.mStride,
                                      SurfaceFormat::B8G8R8A8);
+  if (!dt) {
+    gfxWarning() << "imgTools::EncodeImage failed in CreateDrawTargetForData";
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
   dt->DrawSurface(frame,
                   Rect(0, 0, aScaledWidth, aScaledHeight),
                   Rect(0, 0, frameWidth, frameHeight),
@@ -293,6 +298,10 @@ NS_IMETHODIMP imgTools::EncodeCroppedImage(imgIContainer *aContainer,
                                      dataSurface->GetSize(),
                                      map.mStride,
                                      SurfaceFormat::B8G8R8A8);
+  if (!dt) {
+    gfxWarning() << "imgTools::EncodeCroppedImage failed in CreateDrawTargetForData";
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
   dt->CopySurface(frame,
                   IntRect(aOffsetX, aOffsetY, aWidth, aHeight),
                   IntPoint(0, 0));
diff --git a/js/src/jit/IonTypes.h b/js/src/jit/IonTypes.h
index eb77c5545e..a3cec183e5 100644
--- a/js/src/jit/IonTypes.h
+++ b/js/src/jit/IonTypes.h
@@ -487,6 +487,8 @@ StringFromMIRType(MIRType type)
       return "MagicUninitializedLexical";
     case MIRType_Value:
       return "Value";
+    case MIRType_ObjectOrNull:
+      return "ObjectOrNull";
     case MIRType_None:
       return "None";
     case MIRType_Slots:
@@ -495,10 +497,16 @@ StringFromMIRType(MIRType type)
       return "Elements";
     case MIRType_Pointer:
       return "Pointer";
-    case MIRType_Int32x4:
-      return "Int32x4";
+    case MIRType_Shape:
+      return "Shape";
+    case MIRType_ObjectGroup:
+      return "ObjectGroup";
     case MIRType_Float32x4:
       return "Float32x4";
+    case MIRType_Int32x4:
+      return "Int32x4";
+    case MIRType_Doublex2:
+      return "Doublex2";
     default:
       MOZ_CRASH("Unknown MIRType.");
   }
diff --git a/layout/base/FrameLayerBuilder.cpp b/layout/base/FrameLayerBuilder.cpp
index 4647b5e067..205bc1e9c8 100644
--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@@ -2685,9 +2685,11 @@ PaintInactiveLayer(nsDisplayListBuilder* aBuilder,
     tempDT = gfxPlatform::GetPlatform()->CreateOffscreenContentDrawTarget(
                                       itemVisibleRect.Size().ToIntSize(),
                                       SurfaceFormat::B8G8R8A8);
-    context = new gfxContext(tempDT);
-    context->SetMatrix(gfxMatrix::Translation(-itemVisibleRect.x,
-                                              -itemVisibleRect.y));
+    if (tempDT) {
+      context = new gfxContext(tempDT);
+      context->SetMatrix(gfxMatrix::Translation(-itemVisibleRect.x,
+                                                -itemVisibleRect.y));
+    }
   }
 #endif
   basic->BeginTransaction();
@@ -2709,7 +2711,7 @@ PaintInactiveLayer(nsDisplayListBuilder* aBuilder,
   basic->SetTarget(nullptr);
 
 #ifdef MOZ_DUMP_PAINTING
-  if (gfxUtils::sDumpPainting) {
+  if (gfxUtils::sDumpPainting && tempDT) {
     RefPtr<SourceSurface> surface = tempDT->Snapshot();
     DumpPaintedImage(aItem, surface);
 
diff --git a/toolkit/components/telemetry/Histograms.json b/toolkit/components/telemetry/Histograms.json
index 517cb46825..c1ccab1064 100644
--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -3685,14 +3685,6 @@
     "extended_statistics_ok": true,
     "description": "Session restore: Time to collect all window data (ms)"
   },
-  "FX_SESSION_RESTORE_COLLECT_SINGLE_WINDOW_DATA_MS": {
-    "expires_in_version": "40",
-    "kind": "exponential",
-    "high": "30000",
-    "n_buckets": 10,
-    "extended_statistics_ok": true,
-    "description": "Session restore: Time to collect the data of a single window (ms)"
-  },
   "FX_SESSION_RESTORE_COLLECT_COOKIES_MS": {
     "expires_in_version": "40",
     "kind": "exponential",
@@ -3758,14 +3750,6 @@
     "extended_statistics_ok": true,
     "description": "Session restore: Time spent on the main thread sending the session data off the main thread for writing (ms)"
   },
-  "FX_SESSION_RESTORE_WRITE_STATE_LONGEST_OP_MS": {
-    "expires_in_version": "40",
-    "kind": "exponential",
-    "high": "3000",
-    "n_buckets": 10,
-    "extended_statistics_ok": true,
-    "description": "Session restore: Time spent on the main thread serializing, broadcasting and sending the session data for writing (ms)"
-  },
   "FX_SESSION_RESTORE_WRITE_FILE_MS": {
     "expires_in_version": "default",
     "kind": "exponential",
diff --git a/toolkit/devtools/server/actors/script.js b/toolkit/devtools/server/actors/script.js
index 9073b4c7a8..b5041059d9 100644
--- a/toolkit/devtools/server/actors/script.js
+++ b/toolkit/devtools/server/actors/script.js
@@ -4663,6 +4663,10 @@ BreakpointActor.prototype = {
   actorPrefix: "breakpoint",
   condition: null,
 
+  disconnect: function () {
+    this.removeScripts();
+  },
+
   hasScript: function (aScript) {
     return this.scripts.has(aScript);
   },
diff --git a/toolkit/modules/AddonWatcher.jsm b/toolkit/modules/AddonWatcher.jsm
index d85016db59..d9f0d437e0 100644
--- a/toolkit/modules/AddonWatcher.jsm
+++ b/toolkit/modules/AddonWatcher.jsm
@@ -68,10 +68,7 @@ let AddonWatcher = {
     let limit = this._interval * Preferences.get("browser.addon-watch.percentage-limit", 75) * 10;
     for (let addonId in addons) {
       if (!this._ignoreList.has(addonId)) {
-        if (!this._lastAddonTime[addonId]) {
-          this._lastAddonTime[addonId] = 0;
-        }
-        if ((addons[addonId] - this._lastAddonTime[addonId]) > limit) {
+        if (this._lastAddonTime[addonId] && ((addons[addonId] - this._lastAddonTime[addonId]) > limit)) {
           this._callback(addonId);
         }
         this._lastAddonTime[addonId] = addons[addonId];
diff --git a/toolkit/modules/ResetProfile.jsm b/toolkit/modules/ResetProfile.jsm
index 7f4711c2ba..995ae8147d 100644
--- a/toolkit/modules/ResetProfile.jsm
+++ b/toolkit/modules/ResetProfile.jsm
@@ -6,6 +6,90 @@
 
 this.EXPORTED_SYMBOLS = ["ResetProfile"];
 
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+#expand const MOZ_APP_NAME = "__MOZ_APP_NAME__";
+#expand const MOZ_BUILD_APP = "__MOZ_BUILD_APP__";
+
+Cu.import("resource://gre/modules/Services.jsm");
+
+this.ResetProfile = {
+  /**
+   * Check if reset is supported for the currently running profile.
+   *
+   * @return boolean whether reset is supported.
+   */
+  resetSupported: function() {
+    let profileService = Cc["@mozilla.org/toolkit/profile-service;1"].
+                         getService(Ci.nsIToolkitProfileService);
+    let currentProfileDir = Services.dirsvc.get("ProfD", Ci.nsIFile);
+
+    // Reset is only supported for the default profile if the self-migrator used for reset exists.
+    try {
+      return currentProfileDir.equals(profileService.selectedProfile.rootDir) &&
+        ("@mozilla.org/profile/migrator;1?app=" + MOZ_BUILD_APP + "&type=" + MOZ_APP_NAME in Cc);
+    } catch (e) {
+      // Catch exception when there is no selected profile.
+      Cu.reportError(e);
+    }
+    return false;
+  },
+
+  getMigratedData: function() {
+    Cu.import("resource:///modules/MigrationUtils.jsm");
+
+    // From migration.properties
+    const MIGRATED_TYPES = [
+      128,// Windows/Tabs
+      4,  // History and Bookmarks
+      16, // Passwords
+      8,  // Form History
+      2,  // Cookies
+    ];
+
+    // Loop over possible data to migrate to give the user a list of what will be preserved.
+    let dataTypes = [];
+    for (let itemID of MIGRATED_TYPES) {
+      try {
+        let typeName = MigrationUtils.getLocalizedString(itemID + "_" + MOZ_APP_NAME);
+        dataTypes.push(typeName);
+      } catch (x) {
+        // Catch exceptions when the string for a data type doesn't exist.
+        Cu.reportError(x);
+      }
+    }
+    return dataTypes;
+  },
+
+  /**
+   * Ask the user if they wish to restart the application to reset the profile.
+   */
+  openConfirmationDialog: function(window) {
+    // Prompt the user to confirm.
+    let params = {
+      reset: false,
+    };
+    window.openDialog("chrome://global/content/resetProfile.xul", null,
+                      "chrome,modal,centerscreen,titlebar,dialog=yes", params);
+    if (!params.reset)
+      return;
+
+    // Set the reset profile environment variable.
+    let env = Cc["@mozilla.org/process/environment;1"]
+                .getService(Ci.nsIEnvironment);
+    env.set("MOZ_RESET_PROFILE_RESTART", "1");
+
+    let appStartup = Cc["@mozilla.org/toolkit/app-startup;1"].getService(Ci.nsIAppStartup);
+    appStartup.quit(Ci.nsIAppStartup.eForceQuit | Ci.nsIAppStartup.eRestart);
+  },
+};
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["ResetProfile"];
+
 const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
 //For Pale Moon: Hard-code MOZ_APP_NAME to firefox because of hard-coded type in migrator.
diff --git a/widget/cocoa/nsChildView.mm b/widget/cocoa/nsChildView.mm
index 738bc3bb61..118e1f9581 100644
--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -3455,6 +3455,7 @@ NSEvent* gLastDragMouseDownEvent = nil;
       gfx::Factory::CreateDrawTargetForCairoCGContext(aContext,
                                                       gfx::IntSize(backingSize.width,
                                                                    backingSize.height));
+    MOZ_ASSERT(dt); // see implementation
     dt->AddUserData(&gfxContext::sDontUseAsSourceKey, dt, nullptr);
     targetContext = new gfxContext(dt);
   } else if (gfxPlatform::GetPlatform()->SupportsAzureContentForType(gfx::BackendType::CAIRO)) {
diff --git a/widget/gonk/nsWindow.cpp b/widget/gonk/nsWindow.cpp
index 396325152d..42e3b6c6d2 100644
--- a/widget/gonk/nsWindow.cpp
+++ b/widget/gonk/nsWindow.cpp
@@ -45,6 +45,7 @@
 #include "pixelflinger/format.h"
 #include "mozilla/BasicEvents.h"
 #include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/Logging.h"
 #include "mozilla/layers/APZCTreeManager.h"
 #include "mozilla/layers/APZThreadUtils.h"
 #include "mozilla/layers/CompositorParent.h"
@@ -690,6 +691,9 @@ nsWindow::StartRemoteDrawing()
     mFramebufferTarget = Factory::CreateDrawTargetForData(
          BackendType::CAIRO, (uint8_t*)vaddr,
          IntSize(width, height), mFramebuffer->stride * bytepp, format);
+    if (!mFramebufferTarget) {
+        MOZ_CRASH("nsWindow::StartRemoteDrawing failed in CreateDrawTargetForData");
+    }
     if (!mBackBuffer ||
         mBackBuffer->GetSize() != mFramebufferTarget->GetSize() ||
         mBackBuffer->GetFormat() != mFramebufferTarget->GetFormat()) {
diff --git a/widget/windows/WinUtils.cpp b/widget/windows/WinUtils.cpp
index d3ff133ce5..dcd1e8f0ce 100644
--- a/widget/windows/WinUtils.cpp
+++ b/widget/windows/WinUtils.cpp
@@ -1188,6 +1188,10 @@ AsyncFaviconDataReady::OnComplete(nsIURI *aFaviconURI,
                                        dataSurface->GetSize(),
                                        map.mStride,
                                        dataSurface->GetFormat());
+    if (!dt) {
+      gfxWarning() << "AsyncFaviconDataReady::OnComplete failed in CreateDrawTargetForData";
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
     dt->FillRect(Rect(0, 0, size.width, size.height),
                  ColorPattern(Color(1.0f, 1.0f, 1.0f, 1.0f)));
     dt->DrawSurface(surface,
diff --git a/widget/windows/nsWindowGfx.cpp b/widget/windows/nsWindowGfx.cpp
index 93b178ab1f..b851b2b482 100644
--- a/widget/windows/nsWindowGfx.cpp
+++ b/widget/windows/nsWindowGfx.cpp
@@ -378,6 +378,11 @@ bool nsWindow::OnPaint(HDC aDC, uint32_t aNestingLevel)
             gfxPlatform::GetPlatform()->CreateDrawTargetForSurface(targetSurface,
                                                                    IntSize(paintRect.right - paintRect.left,
                                                                    paintRect.bottom - paintRect.top));
+          if (!dt) {
+            gfxWarning() << "nsWindow::OnPaint failed in CreateDrawTargetForSurface";
+            return false;
+          }
+
           // don't need to double buffer with anything but GDI
           BufferMode doubleBuffering = mozilla::layers::BufferMode::BUFFER_NONE;
           if (IsRenderMode(gfxWindowsPlatform::RENDER_GDI) ||
@@ -615,6 +620,10 @@ nsresult nsWindowGfx::CreateIcon(imgIContainer *aContainer,
                                        dataSurface->GetSize(),
                                        map.mStride,
                                        SurfaceFormat::B8G8R8A8);
+    if (!dt) {
+      gfxWarning() << "nsWindowGfx::CreatesIcon failed in CreateDrawTargetForData";
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
     dt->DrawSurface(surface,
                     Rect(0, 0, iconSize.width, iconSize.height),
                     Rect(0, 0, frameSize.width, frameSize.height),