aura: Clean up compositor initialization/destruction.

content/browser/aura/gpu_process_transport_factory.h

Index: content/browser/aura/gpu_process_transport_factory.h
diff --git a/content/browser/aura/gpu_process_transport_factory.h b/content/browser/aura/gpu_process_transport_factory.h
index 9e40b5c743d5f2073cf6edc647914104e97b67e6..d5e90918b05b8df43ef34eb6c0cbfc8e300bbf29 100644
--- a/content/browser/aura/gpu_process_transport_factory.h
+++ b/content/browser/aura/gpu_process_transport_factory.h
@@ -35,7 +35,7 @@ class GpuProcessTransportFactory
   scoped_ptr<WebGraphicsContext3DCommandBufferImpl>
   CreateOffscreenCommandBufferContext();
 
-  // ImageTransportFactory implementation.
+  // ContextFactory implementation.
   virtual scoped_ptr<WebKit::WebGraphicsContext3D> CreateOffscreenContext()
       OVERRIDE;
   virtual scoped_ptr<cc::OutputSurface> CreateOutputSurface(
@@ -46,6 +46,9 @@ class GpuProcessTransportFactory
   virtual void RemoveReflector(
       scoped_refptr<ui::Reflector> reflector) OVERRIDE;
   virtual void RemoveCompositor(ui::Compositor* compositor) OVERRIDE;
+  virtual bool UsesTestContexts() OVERRIDE;
+
+  // ImageTransportFactory implementation.
   virtual ui::ContextFactory* AsContextFactory() OVERRIDE;
   virtual gfx::GLSurfaceHandle CreateSharedSurfaceHandle() OVERRIDE;
   virtual void DestroySharedSurfaceHandle(