Bug 1043426 - Don't crash when failing to upload apply a maskon a container layer. r=Bas

gfx/layers/composite/ContainerLayerComposite.cpp

@@ -530,6 +530,10 @@ ContainerRender(ContainerT* aContainer,
     LayerManagerComposite::AutoAddMaskEffect autoMaskEffect(aContainer->GetMaskLayer(),
                                                             effectChain,
                                                             !aContainer->GetTransform().CanDraw2D());
+    if (autoMaskEffect.Failed()) {
+      NS_WARNING("Failed to apply a mask effect.");
+      return;
+    }
 
     aContainer->AddBlendModeEffect(effectChain);
     effectChain.mPrimaryEffect = new EffectRenderTarget(surface);

gfx/layers/composite/LayerManagerComposite.h

@@ -184,6 +184,7 @@ public:
                       bool aIs3D = false);
     ~AutoAddMaskEffect();
 
+    bool Failed() const { return !!mCompositable; }
   private:
     CompositableHost* mCompositable;
   };