Bug 1315583 - Release ActiveResourceTracker on the main thread. r=dvander

gfx/layers/ipc/ShadowLayers.cpp

@@ -192,6 +192,21 @@ ShadowLayerForwarder::ShadowLayerForwarder(ClientLayerManager* aClientLayerManag
   mActiveResourceTracker = MakeUnique<ActiveResourceTracker>(1000, "CompositableForwarder");
 }
 
+template<typename T>
+struct ReleaseOnMainThreadTask : public Runnable
+{
+  UniquePtr<T> mObj;
+
+  explicit ReleaseOnMainThreadTask(UniquePtr<T>& aObj)
+    : mObj(Move(aObj))
+  {}
+
+  NS_IMETHOD Run() override {
+    mObj = nullptr;
+    return NS_OK;
+  }
+};
+
 ShadowLayerForwarder::~ShadowLayerForwarder()
 {
   MOZ_ASSERT(mTxn->Finished(), "unfinished transaction?");
@@ -200,6 +215,10 @@ ShadowLayerForwarder::~ShadowLayerForwarder()
     mShadowManager->SetForwarder(nullptr);
     mShadowManager->Destroy();
   }
+  if (!NS_IsMainThread()) {
+    NS_DispatchToMainThread(
+      new ReleaseOnMainThreadTask<ActiveResourceTracker>(mActiveResourceTracker));
+  }
 }
 
 void