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

content/browser/renderer_host/offscreen_canvas_compositor_frame_sink_provider_impl.cc

Index: content/browser/renderer_host/offscreen_canvas_compositor_frame_sink_provider_impl.cc
diff --git a/content/browser/renderer_host/offscreen_canvas_compositor_frame_sink_provider_impl.cc b/content/browser/renderer_host/offscreen_canvas_compositor_frame_sink_provider_impl.cc
index abd15c636fde412a497e1a6f02de96d7170332ca..4bc06e0e61ab677caf8fe60387e0358575433d6b 100644
--- a/content/browser/renderer_host/offscreen_canvas_compositor_frame_sink_provider_impl.cc
+++ b/content/browser/renderer_host/offscreen_canvas_compositor_frame_sink_provider_impl.cc
@@ -7,6 +7,7 @@
 #include "base/memory/ptr_util.h"
 #include "content/browser/compositor/surface_utils.h"
 #include "content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h"
+#include "content/browser/renderer_host/offscreen_canvas_surface_manager.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 
 namespace content {
@@ -29,6 +30,9 @@ void OffscreenCanvasCompositorFrameSinkProviderImpl::CreateCompositorFrameSink(
   compositor_frame_sinks_[frame_sink_id] =
       base::MakeUnique<OffscreenCanvasCompositorFrameSink>(
           this, frame_sink_id, std::move(request), std::move(client));
+
+  OffscreenCanvasSurfaceManager::GetInstance()->RegisterFrameSinkToParent(
+      frame_sink_id);
 }
 
 cc::SurfaceManager*
@@ -39,7 +43,15 @@ OffscreenCanvasCompositorFrameSinkProviderImpl::GetSurfaceManager() {
 void OffscreenCanvasCompositorFrameSinkProviderImpl::
     OnCompositorFrameSinkClientConnectionLost(
         const cc::FrameSinkId& frame_sink_id) {
+  // TODO(fsamuel, xlai): Investigate why this function is not fired when user
+  // close down the window that has OffscreenCanvas commit().
   compositor_frame_sinks_.erase(frame_sink_id);
 }
 
+void OffscreenCanvasCompositorFrameSinkProviderImpl::
+    OnCompositorFrameSinkClientDestroyed(const cc::FrameSinkId& frame_sink_id) {
+  OffscreenCanvasSurfaceManager::GetInstance()->UnregisterFrameSinkFromParent(
+      frame_sink_id);
+}
+
 }  // namespace content