sync compositor: Send ipc reply in swap

content/browser/android/in_process/synchronous_compositor_impl.h

Index: content/browser/android/in_process/synchronous_compositor_impl.h
diff --git a/content/browser/android/in_process/synchronous_compositor_impl.h b/content/browser/android/in_process/synchronous_compositor_impl.h
index f0a3d82f95a54ef32fb882bd44a5b0414b4a2a41..e5a14611d8c3079fd3b7e5e36cf87e014bd9aeec 100644
--- a/content/browser/android/in_process/synchronous_compositor_impl.h
+++ b/content/browser/android/in_process/synchronous_compositor_impl.h
@@ -60,6 +60,7 @@ class SynchronousCompositorImpl
 
   // SynchronousCompositorOutputSurfaceClient overrides.
   void Invalidate() override;
+  void SwapBuffers(cc::CompositorFrame* frame) override;
 
   // SynchronousCompositor overrides.
   scoped_ptr<cc::CompositorFrame> DemandDrawHw(
@@ -117,6 +118,7 @@ class SynchronousCompositorImpl
   bool is_active_;
   bool renderer_needs_begin_frames_;
   bool need_animate_input_;
+  scoped_ptr<cc::CompositorFrame> frame_holder_;
 
   base::WeakPtrFactory<SynchronousCompositorImpl> weak_ptr_factory_;