Throttle frames in OffscreenCanvasFrameDispatcherImpl

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

 // 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 "platform/graphics/OffscreenCanvasFrameDispatcherImpl.h"
 
 #include "cc/output/compositor_frame.h"
 #include "cc/quads/texture_draw_quad.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "platform/CrossThreadFunctional.h"
@@ skipping 381 matching lines @@
       break;
     case kOffscreenCanvasCommitTypeCount:
       NOTREACHED();
   }
 
   if (change_size_for_next_commit_) {
     current_local_surface_id_ = local_surface_id_allocator_.GenerateId();
     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.

 }
 
 void OffscreenCanvasFrameDispatcherImpl::SetNeedsBeginFrame(
     bool needs_begin_frame) {
   if (sink_ && needs_begin_frame != needs_begin_frame_) {
     needs_begin_frame_ = needs_begin_frame;
     sink_->SetNeedsBeginFrame(needs_begin_frame);
   }
 }
 
 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 =
       cc::BeginFrameArgs::kInvalidFrameNumber;
 }
 
 void OffscreenCanvasFrameDispatcherImpl::ReclaimResources(
     const cc::ReturnedResourceArray& resources) {
   for (const auto& resource : resources) {
     RefPtr<StaticBitmapImage> image = cached_images_.at(resource.id);
@@ skipping 41 matching lines @@
 
 void OffscreenCanvasFrameDispatcherImpl::Reshape(int width, int height) {
   if (width_ != width || height_ != height) {
     width_ = width;
     height_ = height;
     change_size_for_next_commit_ = true;
   }
 }
 
 }  // namespace blink