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

third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.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/CanvasSurfaceLayerBridge.h"
 
 #include "cc/layers/layer.h"
 #include "cc/layers/solid_color_layer.h"
 #include "cc/layers/surface_layer.h"
 #include "cc/surfaces/sequence_surface_reference_factory.h"
 #include "cc/surfaces/surface_id.h"
 #include "cc/surfaces/surface_info.h"
 #include "cc/surfaces/surface_sequence.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/mojo/MojoHelper.h"
 #include "public/platform/InterfaceProvider.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebCompositorSupport.h"
 #include "public/platform/WebLayer.h"
+#include "public/platform/WebLayerTreeView.h"
 #include "public/platform/modules/offscreencanvas/offscreen_canvas_surface.mojom-blink.h"
 #include "ui/gfx/geometry/size.h"
 #include "wtf/Functional.h"
 
 namespace blink {
 
 namespace {
 
 class OffscreenCanvasSurfaceReferenceFactory
     : public cc::SequenceSurfaceReferenceFactory {
@@ skipping 18 matching lines @@
   }
 
   base::WeakPtr<CanvasSurfaceLayerBridge> m_bridge;
 
   DISALLOW_COPY_AND_ASSIGN(OffscreenCanvasSurfaceReferenceFactory);
 };
 
 }  // namespace
 
 CanvasSurfaceLayerBridge::CanvasSurfaceLayerBridge(
-    CanvasSurfaceLayerBridgeObserver* observer)
+    CanvasSurfaceLayerBridgeObserver* observer,
+    WebLayerTreeView* layerTreeView)
     : m_weakFactory(this),
       m_observer(observer),
       m_binding(this),
-      m_frameSinkId(Platform::current()->generateFrameSinkId()) {
+      m_frameSinkId(Platform::current()->generateFrameSinkId()),
+      m_parentFrameSinkId(layerTreeView ? layerTreeView->getFrameSinkId()

[dcheng, 2017/01/24 22:31:37]

With the latest PS, do we still need a null check here?

[xlai (Olivia), 2017/01/24 22:57:12]

Yes, in EmptyChromeClient or Unit test, layertreeview can be nullptr.

[xlai (Olivia), 2017/01/24 23:15:39]

I took away the nullity check. I look through the instances that make
use of EmptyChromeClient and cannot think of a case when a canvas element that
has transfercontrol to offscreen appearing there.

+                                        : cc::FrameSinkId()) {
   m_refFactory =
       new OffscreenCanvasSurfaceReferenceFactory(m_weakFactory.GetWeakPtr());
 
   DCHECK(!m_service.is_bound());
   mojom::blink::OffscreenCanvasSurfaceFactoryPtr serviceFactory;
   Platform::current()->interfaceProvider()->getInterface(
       mojo::MakeRequest(&serviceFactory));
+  // TODO(xlai): Ensure OffscreenCanvas commit() is still functional when a
+  // frame-less HTML canvas's document is reparenting under another frame.
+  // See crbug.com/683172.
   serviceFactory->CreateOffscreenCanvasSurface(
-      m_frameSinkId, m_binding.CreateInterfacePtrAndBind(),
+      m_parentFrameSinkId, m_frameSinkId, m_binding.CreateInterfacePtrAndBind(),
       mojo::MakeRequest(&m_service));
 }
 
 CanvasSurfaceLayerBridge::~CanvasSurfaceLayerBridge() {
   m_observer = nullptr;
 }
 
 void CanvasSurfaceLayerBridge::createSolidColorLayer() {
   m_CCLayer = cc::SolidColorLayer::Create();
   m_CCLayer->SetBackgroundColor(SK_ColorTRANSPARENT);
@@ skipping 38 matching lines @@
   m_service->Satisfy(sequence);
 }
 
 void CanvasSurfaceLayerBridge::requireCallback(
     const cc::SurfaceId& surfaceId,
     const cc::SurfaceSequence& sequence) {
   m_service->Require(surfaceId, sequence);
 }
 
 }  // namespace blink