Backed out changeset 405a715a4d81 from bug 502307 due to test failures

browser/base/content/browser.js

@@ -5719,17 +5719,13 @@ function warnAboutClosingWindow() {
   os.notifyObservers(null, "browser-lastwindow-close-granted", null);
 
 #ifdef XP_MACOSX
-  // On OS X, always warn about closing multiple tabs, as closing the
-  // last window won't quit the application.
+  // OS X doesn't quit the application when the last window is closed, but keeps
+  // the session alive. Hence don't prompt users to save tabs, but warn about
+  // closing multiple tabs.
+  return gBrowser.warnAboutClosingTabs(true);
 #else
-  // If we're inside auto-started private browsing mode, always warn
-  // about closing multiple tabs (bug 502307).
-  if (gPrivateBrowsingUI.privateBrowsingEnabled &&
-      gPrivateBrowsingUI.autoStarted)
-#endif
-    return gBrowser.warnAboutClosingTabs(true);
-
   return true;
+#endif
 }
 
 var MailIntegration = {
@@ -7042,10 +7038,6 @@ let gPrivateBrowsingUI = {
 
   get privateBrowsingEnabled PBUI_get_privateBrowsingEnabled() {
     return this._privateBrowsingService.privateBrowsingEnabled;
-  },
-
-  get autoStarted PBUI_get_autoStarted() {
-    return this._privateBrowsingService.autoStarted;
   }
 };
 

toolkit/content/globalOverlay.js

@@ -13,18 +13,19 @@ function closeWindow(aClose, aPromptFunction)
       break;
   }
 
-  var showPromptOverride = false;
-  if ("@mozilla.org/privatebrowsing;1" in Components.classes) {
+  var inPrivateBrowsing = false;
+  try {
     var pbSvc = Components.classes["@mozilla.org/privatebrowsing;1"]
                           .getService(Components.interfaces.nsIPrivateBrowsingService);
-    showPromptOverride = pbSvc.privateBrowsingEnabled &&
-                         pbSvc.autoStarted;
+    inPrivateBrowsing = pbSvc.privateBrowsingEnabled;
+  } catch(e) {
+    // safe to ignore
   }
 
   // If we're down to the last window and someone tries to shut down, check to make sure we can!
   if (windowCount == 1 && !canQuitApplication())
     return false;
-  else if (windowCount != 1 || showPromptOverride)
+  else if (windowCount != 1 || inPrivateBrowsing)
 #endif
     if (typeof(aPromptFunction) == "function" && !aPromptFunction())
       return false;