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

content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.cc

 // Copyright 2016 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.
 
 #include "content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h"
 
 #include "base/memory/ptr_util.h"
 #include "cc/surfaces/surface.h"
 #include "cc/surfaces/surface_manager.h"
 #include "content/browser/renderer_host/offscreen_canvas_compositor_frame_sink_provider_impl.h"
+#include "content/browser/renderer_host/offscreen_canvas_surface_manager.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 
 namespace content {
 
 OffscreenCanvasCompositorFrameSink::OffscreenCanvasCompositorFrameSink(
     OffscreenCanvasCompositorFrameSinkProviderImpl* provider,
     const cc::FrameSinkId& frame_sink_id,
     cc::mojom::MojoCompositorFrameSinkRequest request,
     cc::mojom::MojoCompositorFrameSinkClientPtr client)
     : provider_(provider),
       support_(this,
                provider->GetSurfaceManager(),
                frame_sink_id,
                nullptr,
                nullptr),
       client_(std::move(client)),
       binding_(this, std::move(request)) {
   binding_.set_connection_error_handler(
       base::Bind(&OffscreenCanvasCompositorFrameSink::OnClientConnectionLost,
                  base::Unretained(this)));
+
+  OffscreenCanvasSurfaceManager::GetInstance()->RegisterFrameSinkToItsParent(

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

Maybe move this to
OffscreenCanvasCompositorFrameSinkProviderImpl::CreateCompositorFrameSink?

The reason being I want this class to continue to look like
GpuCompositorFrameSink so we can merge those two soon.

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

Done.

+      frame_sink_id);
 }
 
-OffscreenCanvasCompositorFrameSink::~OffscreenCanvasCompositorFrameSink() {}
+OffscreenCanvasCompositorFrameSink::~OffscreenCanvasCompositorFrameSink() {
+  OffscreenCanvasSurfaceManager::GetInstance()
+      ->UnregisterFrameSinkFromItsParent(support_.frame_sink_id());

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

Maybe move this to
OffscreenCanvasCompositorFrameSinkProviderImpl::OnCompositorFrameSinkClientConnectionLost?

The reason being I want this class to continue to look like
GpuCompositorFrameSink so we can merge those two soon.

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

Simply moving this to OnCompositorFrameSinkClientConnectionLost will not work,
because OnCompositorFrameSinkClientConnectionLost is not fired when
OffscreenCanvasCompositorFrameSink is destroyed normally (i.e. closing down the
window), which will then result in assert failure in SurfaceManager's
destructor.

My workaround is to introduce
OffscreenCanvasCompositorFrameSinkProviderImpl::OnCompositorFrameSinkClientDestroyed
and call that when compositorframesink is destroyed. With that, I can avoid
seeing the assert error when I close down the window.

+}
 
 void OffscreenCanvasCompositorFrameSink::SetNeedsBeginFrame(
     bool needs_begin_frame) {
   support_.SetNeedsBeginFrame(needs_begin_frame);
 }
 
 void OffscreenCanvasCompositorFrameSink::SubmitCompositorFrame(
     const cc::LocalFrameId& local_frame_id,
     cc::CompositorFrame frame) {
   support_.SubmitCompositorFrame(local_frame_id, std::move(frame));
@@ skipping 47 matching lines @@
   if (client_)
     client_->WillDrawSurface();
 }
 
 void OffscreenCanvasCompositorFrameSink::OnClientConnectionLost() {
   provider_->OnCompositorFrameSinkClientConnectionLost(
       support_.frame_sink_id());
 }
 
 }  // namespace content