sync compositor: Reduce begin frame sync IPC overhead

content/browser/android/synchronous_compositor_host.h

Index: content/browser/android/synchronous_compositor_host.h
diff --git a/content/browser/android/synchronous_compositor_host.h b/content/browser/android/synchronous_compositor_host.h
index f5e6d2b519d64639cba424a7e7160222ee1edcfd..aa6fa75595d608a4e4a4fb642a4d9b20ca363d65 100644
--- a/content/browser/android/synchronous_compositor_host.h
+++ b/content/browser/android/synchronous_compositor_host.h
@@ -32,10 +32,15 @@ namespace cc {
 struct BeginFrameArgs;
 }
 
+namespace ui {
+class WindowAndroid;
+}
+
 namespace content {
 
 class RenderWidgetHostViewAndroid;
 class SynchronousCompositorClient;
+class SynchronousCompositorObserver;
 class WebContents;
 struct DidOverscrollParams;
 struct SyncCompositorCommonRendererParams;
@@ -66,9 +71,13 @@ class SynchronousCompositorHost : public SynchronousCompositor {
   void OnComputeScroll(base::TimeTicks animation_time) override;
 
   void DidOverscroll(const DidOverscrollParams& over_scroll_params);
-  void DidSendBeginFrame();
+  void DidSendBeginFrame(ui::WindowAndroid* window_android);
   bool OnMessageReceived(const IPC::Message& message);
 
+  // Called by SynchronousCompositorObserver.
+  int routing_id() const { return routing_id_; }
+  void ProcessCommonParams(const SyncCompositorCommonRendererParams& params);
+
  private:
   class ScopedSendZeroMemory;
   struct SharedMemoryWithSize;
@@ -78,7 +87,6 @@ class SynchronousCompositorHost : public SynchronousCompositor {
   SynchronousCompositorHost(RenderWidgetHostViewAndroid* rwhva,
                             SynchronousCompositorClient* client,
                             bool use_in_proc_software_draw);
-  void ProcessCommonParams(const SyncCompositorCommonRendererParams& params);
   void UpdateFrameMetaData(cc::CompositorFrameMetadata frame_metadata);
   void OutputSurfaceCreated();
   bool DemandDrawSwInProc(SkCanvas* canvas);
@@ -90,6 +98,7 @@ class SynchronousCompositorHost : public SynchronousCompositor {
   const scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
   const int process_id_;
   const int routing_id_;
+  SynchronousCompositorObserver* const rph_observer_;
   IPC::Sender* const sender_;
   const bool use_in_process_zero_copy_software_draw_;