Enable the Sky compositor again

sky/compositor/surface_holder.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SKY_COMPOSITOR_SURFACE_HOLDER_H_
 #define SKY_COMPOSITOR_SURFACE_HOLDER_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "mojo/services/public/interfaces/surfaces/surface_id.mojom.h"
@@ skipping 16 matching lines @@
     virtual void ReturnResources(
         mojo::Array<mojo::ReturnedResourcePtr> resources) = 0;
 
    protected:
     virtual ~Client();
   };
 
   explicit SurfaceHolder(Client* client, mojo::Shell* shell);
   ~SurfaceHolder() override;
 
+  bool IsReadyForFrame() const;
+
   void SetSize(const gfx::Size& size);
   void SubmitFrame(mojo::FramePtr frame);
 
  private:
   // mojo::SurfaceClient
   void ReturnResources(
       mojo::Array<mojo::ReturnedResourcePtr> resources) override;
 
   void OnSurfaceConnectionCreated(mojo::SurfacePtr surface,
                                   uint32_t id_namespace);
 
   Client* client_;
   gfx::Size size_;
   scoped_ptr<SurfaceAllocator> surface_allocator_;
   mojo::SurfacesServicePtr surfaces_service_;
   mojo::SurfacePtr surface_;
   mojo::SurfaceIdPtr surface_id_;
 
   base::WeakPtrFactory<SurfaceHolder> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceHolder);
 };
 
 }  // namespace sky
 
 #endif  // SKY_COMPOSITOR_SURFACE_HOLDER_H_