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

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

Index: third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp b/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
index 67b4817b97fb74df518a102fd71c098bde45f26c..a646fae9aba638c8ae39ee9747f8eb47c6417fba 100644
--- a/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
+++ b/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
@@ -17,6 +17,7 @@
 #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"
@@ -55,11 +56,14 @@ class 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());
 
@@ -67,8 +71,11 @@ CanvasSurfaceLayerBridge::CanvasSurfaceLayerBridge(
   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));
 }