aura: Defer OutputSurface creation until widget is available

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index fe2a0339814927d6d6f41c484f88a84fb7ba7801..8235c453df32750dc77f1e5265270089c4029c6b 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -230,8 +230,8 @@ class COMPOSITOR_EXPORT Compositor
   void SetAuthoritativeVSyncInterval(const base::TimeDelta& interval);
 
   // Sets the widget for the compositor to render into.
-  void SetAcceleratedWidgetAndStartCompositor(gfx::AcceleratedWidget widget);
-  gfx::AcceleratedWidget widget() const { return widget_; }
+  void SetAcceleratedWidget(gfx::AcceleratedWidget widget);
+  gfx::AcceleratedWidget widget() const;
 
   // Returns the vsync manager for this compositor.
   scoped_refptr<CompositorVSyncManager> vsync_manager() const;
@@ -343,6 +343,8 @@ class COMPOSITOR_EXPORT Compositor
   std::list<CompositorBeginFrameObserver*> begin_frame_observer_list_;
 
   gfx::AcceleratedWidget widget_;
+  bool widget_valid_;
+  bool output_surface_requested_;
   scoped_ptr<cc::SurfaceIdAllocator> surface_id_allocator_;
   scoped_refptr<cc::Layer> root_web_layer_;
   scoped_ptr<cc::LayerTreeHost> host_;