Make cc output surface creation async

cc/trees/proxy.h

Index: cc/trees/proxy.h
diff --git a/cc/trees/proxy.h b/cc/trees/proxy.h
index 8d72728cfe07bd5cc2820f2a0e91bfcfb6c41c5e..feeab43b507603a43c8bf66d3338cb4685cb0c90 100644
--- a/cc/trees/proxy.h
+++ b/cc/trees/proxy.h
@@ -57,6 +57,10 @@ class CC_EXPORT Proxy {
 
   virtual bool IsStarted() const = 0;
 
+  // Will call LayerTreeHost::OnCreateAndInitializeOutputSurfaceAttempted
+  // with the result of this function.
+  virtual void SetOutputSurface(scoped_ptr<OutputSurface> output_surface) = 0;
+
   // Indicates that the compositing surface associated with our context is
   // ready to use.
   virtual void SetLayerTreeHostClientReady() = 0;