Make OffscreenCanvas animation in sync with its placeholder canvas's parent frame rate

content/browser/renderer_host/offscreen_canvas_surface_manager.cc

Index: content/browser/renderer_host/offscreen_canvas_surface_manager.cc
diff --git a/content/browser/renderer_host/offscreen_canvas_surface_manager.cc b/content/browser/renderer_host/offscreen_canvas_surface_manager.cc
index 65ff06e0c83c3e60eaf4e6a0e92eb6a283f56809..82301b60d4a07fdf720bfc6595d8a1ee16a11944 100644
--- a/content/browser/renderer_host/offscreen_canvas_surface_manager.cc
+++ b/content/browser/renderer_host/offscreen_canvas_surface_manager.cc
@@ -27,6 +27,30 @@ OffscreenCanvasSurfaceManager* OffscreenCanvasSurfaceManager::GetInstance() {
   return g_manager.Pointer();
 }
 
+void OffscreenCanvasSurfaceManager::RegisterFrameSinkToItsParent(

[Fady Samuel, 2017/01/19 04:05:43]

nit: RegisterFrameSinkToParent?

[xlai (Olivia), 2017/01/19 16:43:56]

Done.

+    cc::FrameSinkId child_frame_sink_id) {

[Fady Samuel, 2017/01/19 04:05:43]

nit: const cc::FrameSinkId&

[xlai (Olivia), 2017/01/19 16:43:56]

Done.

+  auto surface_iter = registered_surface_instances_.find(child_frame_sink_id);
+  if (surface_iter == registered_surface_instances_.end())
+    return;
+  OffscreenCanvasSurfaceImpl* surfaceImpl = surface_iter->second;
+  if (surfaceImpl->parent_frame_sink_id().is_valid()) {
+    GetSurfaceManager()->RegisterFrameSinkHierarchy(
+        surfaceImpl->parent_frame_sink_id(), child_frame_sink_id);
+  }
+}
+
+void OffscreenCanvasSurfaceManager::UnregisterFrameSinkFromItsParent(

[Fady Samuel, 2017/01/19 04:05:43]

nit: UnregisterFrameSinkFromParent?

[xlai (Olivia), 2017/01/19 16:43:56]

Done.

+    cc::FrameSinkId child_frame_sink_id) {

[Fady Samuel, 2017/01/19 04:05:43]

const cc::FrameSinkId&

[xlai (Olivia), 2017/01/19 16:43:56]

Done.

+  auto surface_iter = registered_surface_instances_.find(child_frame_sink_id);
+  if (surface_iter == registered_surface_instances_.end())
+    return;
+  OffscreenCanvasSurfaceImpl* surfaceImpl = surface_iter->second;
+  if (surfaceImpl->parent_frame_sink_id().is_valid()) {
+    GetSurfaceManager()->UnregisterFrameSinkHierarchy(
+        surfaceImpl->parent_frame_sink_id(), child_frame_sink_id);
+  }
+}
+
 void OffscreenCanvasSurfaceManager::OnSurfaceCreated(
     const cc::SurfaceInfo& surface_info) {
   auto surface_iter =