Bug 951120 - Don't process native events on the main thread during xpcom shutdown in metro widget. r=bbondy

widget/windows/winrt/MetroApp.cpp

@@ -42,6 +42,7 @@ namespace winrt {
 ComPtr<FrameworkView> sFrameworkView;
 ComPtr<MetroApp> sMetroApp;
 ComPtr<ICoreApplication> sCoreApp;
+bool MetroApp::sGeckoShuttingDown = false;
 
 ////////////////////////////////////////////////////
 // IFrameworkViewSource impl.
@@ -109,6 +110,8 @@ MetroApp::ShutdownXPCOM()
     sFrameworkView->ShutdownXPCOM();
   }
 
+  MetroApp::sGeckoShuttingDown = true;
+
   // Shut down xpcom
   XRE_metroShutdown();
 

widget/windows/winrt/MetroApp.h

@@ -46,6 +46,8 @@ public:
   void CoreExit();
 
   void ShutdownXPCOM();
+  // Set when gecko enters xpcom shutdown.
+  static bool sGeckoShuttingDown;
 
   // Shared pointers between framework and widget
   static void SetBaseWidget(MetroWidget* aPtr);

widget/windows/winrt/MetroAppShell.cpp

@@ -324,8 +324,8 @@ MetroAppShell::InputEventsDispatched()
 void
 MetroAppShell::DispatchAllGeckoEvents()
 {
-  // Only do this if requested
-  if (!sShouldPurgeThreadQueue) {
+  // Only do this if requested and when we're not shutting down
+  if (!sShouldPurgeThreadQueue || MetroApp::sGeckoShuttingDown) {
     return;
   }
 
@@ -414,6 +414,15 @@ void
 MetroAppShell::NativeCallback()
 {
   NS_ASSERTION(NS_IsMainThread(), "Native callbacks must be on the metro main thread");
+
+  // We shouldn't process native events during xpcom shutdown - this can
+  // trigger unexpected xpcom event dispatching for the main thread when
+  // the thread manager is in the process of shutting down non-main threads,
+  // resulting in shutdown hangs.
+  if (MetroApp::sGeckoShuttingDown) {
+    return;
+  }
+
   NativeEventCallback();
 }