Bug 1316221 - Force VideoBridge shutdown to happen before the compositor thread is destroyed. r=dvander

dom/media/ipc/VideoDecoderManagerParent.cpp

@@ -17,6 +17,7 @@
 #include "mozilla/layers/VideoBridgeChild.h"
 #include "mozilla/SharedThreadPool.h"
 #include "mozilla/layers/ImageDataSerializer.h"
+#include "mozilla/SyncRunnable.h"
 
 #if XP_WIN
 #include <objbase.h>
@@ -103,13 +104,21 @@ VideoDecoderManagerParent::ShutdownThreads()
   sManagerTaskQueue->AwaitShutdownAndIdle();
   sManagerTaskQueue = nullptr;
 
-  sVideoDecoderManagerThread->Dispatch(NS_NewRunnableFunction([]() {
-    layers::VideoBridgeChild::Shutdown();
-  }), NS_DISPATCH_SYNC);
   sVideoDecoderManagerThread->Shutdown();
   sVideoDecoderManagerThread = nullptr;
 }
 
+void
+VideoDecoderManagerParent::ShutdownVideoBridge()
+{
+  if (sVideoDecoderManagerThread) {
+    RefPtr<Runnable> task = NS_NewRunnableFunction([]() {
+      VideoBridgeChild::Shutdown();
+    });
+    SyncRunnable::DispatchToThread(sVideoDecoderManagerThread, task);
+  }
+}
+
 bool
 VideoDecoderManagerParent::OnManagerThread()
 {

dom/media/ipc/VideoDecoderManagerParent.h

@@ -24,6 +24,8 @@ public:
   static void StartupThreads();
   static void ShutdownThreads();
 
+  static void ShutdownVideoBridge();
+
   bool OnManagerThread();
 
 protected:

gfx/ipc/GPUParent.cpp

@@ -22,6 +22,7 @@
 #include "mozilla/dom/VideoDecoderManagerParent.h"
 #include "mozilla/layers/CompositorThread.h"
 #include "mozilla/layers/ImageBridgeParent.h"
+#include "mozilla/dom/VideoDecoderManagerChild.h"
 #include "mozilla/layers/LayerTreeOwnerTracker.h"
 #include "nsDebugImpl.h"
 #include "nsExceptionHandler.h"
@@ -368,6 +369,7 @@ GPUParent::ActorDestroy(ActorDestroyReason aWhy)
     mVsyncBridge->Shutdown();
     mVsyncBridge = nullptr;
   }
+  dom::VideoDecoderManagerParent::ShutdownVideoBridge();
   CompositorThreadHolder::Shutdown();
   Factory::ShutDown();
 #if defined(XP_WIN)

gfx/layers/ipc/VideoBridgeChild.cpp

@@ -30,9 +30,10 @@ VideoBridgeChild::Startup()
 /* static */ void
 VideoBridgeChild::Shutdown()
 {
+  if (sVideoBridgeChildSingleton) {
     sVideoBridgeChildSingleton->Close();
     sVideoBridgeChildSingleton = nullptr;
-
+  }
 }
 
 VideoBridgeChild::VideoBridgeChild()