Don't attach shadowable layers if IPDL fails to construct an actor. (bug 1314349, r=mattwoodrow)

gfx/layers/ipc/ShadowLayerChild.cpp

@@ -12,20 +12,27 @@
 namespace mozilla {
 namespace layers {
 
-ShadowLayerChild::ShadowLayerChild(ShadowableLayer* aLayer)
-  : mLayer(aLayer)
+ShadowLayerChild::ShadowLayerChild()
+  : mLayer(nullptr)
 { }
 
 ShadowLayerChild::~ShadowLayerChild()
 { }
 
+void
+ShadowLayerChild::SetShadowableLayer(ShadowableLayer* aLayer)
+{
+  MOZ_ASSERT(!mLayer);
+  mLayer = aLayer;
+}
+
 void
 ShadowLayerChild::ActorDestroy(ActorDestroyReason why)
 {
   MOZ_ASSERT(AncestorDeletion != why,
              "shadowable layer should have been cleaned up by now");
 
-  if (AbnormalShutdown == why) {
+  if (AbnormalShutdown == why && mLayer) {
     // This is last-ditch emergency shutdown.  Just have the layer
     // forget its IPDL resources; IPDL-generated code will clean up
     // automatically in this case.

gfx/layers/ipc/ShadowLayerChild.h

@@ -20,9 +20,10 @@ class ShadowableLayer;
 class ShadowLayerChild : public PLayerChild
 {
 public:
-  explicit ShadowLayerChild(ShadowableLayer* aLayer);
+  ShadowLayerChild();
   virtual ~ShadowLayerChild();
 
+  void SetShadowableLayer(ShadowableLayer* aLayer);
   ShadowableLayer* layer() const { return mLayer; }
 
 protected:

gfx/layers/ipc/ShadowLayers.cpp

@@ -749,7 +749,14 @@ ShadowLayerForwarder::ConstructShadowFor(ShadowableLayer* aLayer)
   if (!IPCOpen()) {
     return nullptr;
   }
-  return mShadowManager->SendPLayerConstructor(new ShadowLayerChild(aLayer));
+
+  ShadowLayerChild* child = new ShadowLayerChild();
+  if (!mShadowManager->SendPLayerConstructor(child)) {
+    return nullptr;
+  }
+
+  child->SetShadowableLayer(aLayer);
+  return child;
 }
 
 #if !defined(MOZ_HAVE_PLATFORM_SPECIFIC_LAYER_BUFFERS)