Bug 737437 - Destroy the compositor's layer manager before the CompositorChild gets destroyed. r=cjones

gfx/layers/ipc/CompositorParent.cpp

@@ -78,14 +78,24 @@ CompositorParent::Destroy()
   NS_ABORT_IF_FALSE(ManagedPLayersParent().Length() == 0,
                     "CompositorParent destroyed before managed PLayersParent");
 
-  // Ensure that the layer manager is destroyed on the compositor thread.
+  // Ensure that the layer manager is destructed on the compositor thread.
   mLayerManager = NULL;
 }
 
+bool
+CompositorParent::RecvWillStop()
+{
+  mPaused = true;
+
+  // Ensure that the layer manager is destroyed before CompositorChild.
+  mLayerManager->Destroy();
+
+  return true;
+}
+
 bool
 CompositorParent::RecvStop()
 {
-  mPaused = true;
   Destroy();
   return true;
 }

gfx/layers/ipc/CompositorParent.h

@@ -93,6 +93,7 @@ public:
   CompositorParent(nsIWidget* aWidget, base::Thread* aCompositorThread);
   virtual ~CompositorParent();
 
+  virtual bool RecvWillStop() MOZ_OVERRIDE;
   virtual bool RecvStop() MOZ_OVERRIDE;
   virtual bool RecvPause() MOZ_OVERRIDE;
   virtual bool RecvResume() MOZ_OVERRIDE;

gfx/layers/ipc/PCompositor.ipdl

@@ -61,7 +61,10 @@ rpc protocol PCompositor
 
 parent:  
 
-  // Clean up in preparation for destruction.
+  // The child is about to be destroyed, so perform any necessary cleanup.
+  sync WillStop();
+
+  // Clean up in preparation for own destruction.
   sync Stop();
 
   // Pause/resume the compositor. These are intended to be used on mobile, when

widget/xpwidgets/nsBaseWidget.cpp

@@ -153,6 +153,8 @@ nsBaseWidget::~nsBaseWidget()
   }
 
   if (mCompositorChild) {
+    mCompositorChild->SendWillStop();
+    MessageLoop::current()->RunAllPending();
     mCompositorChild->Destroy();
     delete mCompositorThread;
   }