Throttle frames in OffscreenCanvasFrameDispatcherImpl

third_party/WebKit/Source/platform/graphics/OffscreenCanvasFrameDispatcherImpl.cpp

Index: third_party/WebKit/Source/platform/graphics/OffscreenCanvasFrameDispatcherImpl.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/OffscreenCanvasFrameDispatcherImpl.cpp b/third_party/WebKit/Source/platform/graphics/OffscreenCanvasFrameDispatcherImpl.cpp
index c4c1429966dd7fb90c0825a49d02a2a6fce45c50..b66f140d552c7c33c5955302b8efdb1d9c54d529 100644
--- a/third_party/WebKit/Source/platform/graphics/OffscreenCanvasFrameDispatcherImpl.cpp
+++ b/third_party/WebKit/Source/platform/graphics/OffscreenCanvasFrameDispatcherImpl.cpp
@@ -399,12 +399,14 @@ void OffscreenCanvasFrameDispatcherImpl::DispatchFrame(
     change_size_for_next_commit_ = false;
   }
 
+  compositor_has_pending_frame_ = true;
   sink_->SubmitCompositorFrame(current_local_surface_id_, std::move(frame));
 }
 
 void OffscreenCanvasFrameDispatcherImpl::DidReceiveCompositorFrameAck(
     const cc::ReturnedResourceArray& resources) {
   ReclaimResources(resources);
+  compositor_has_pending_frame_ = false;
   // TODO(fsamuel): Implement this.

[Eric Seckler, 2017/04/12 19:39:18]

Is there more to do here? If so, let's update this comment to reflect what's
missing, otherwise remove it.

 }
 
@@ -419,10 +421,19 @@ void OffscreenCanvasFrameDispatcherImpl::SetNeedsBeginFrame(
 void OffscreenCanvasFrameDispatcherImpl::OnBeginFrame(
     const cc::BeginFrameArgs& begin_frame_args) {
   DCHECK(Client());
+
   // TODO(eseckler): Set correct |latest_confirmed_sequence_number|.
   current_begin_frame_ack_ = cc::BeginFrameAck(
       begin_frame_args.source_id, begin_frame_args.sequence_number,
       begin_frame_args.sequence_number, false);
+
+  if (compositor_has_pending_frame_ ||
+      (begin_frame_args.type == cc::BeginFrameArgs::MISSED &&
+       base::TimeTicks::Now() > begin_frame_args.deadline)) {
+    sink_->BeginFrameDidNotSwap(current_begin_frame_ack_);
+    return;
+  }
+
   Client()->BeginFrame();
   // TODO(eseckler): Tell |m_sink| if we did not draw during the BeginFrame.
   current_begin_frame_ack_.sequence_number =