Implementing promise-based commit for driving OffscreenCanvas animations

third_party/WebKit/Source/platform/graphics/OffscreenCanvasFrameDispatcher.h

 // 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.
 
 #ifndef OffscreenCanvasFrameDispatcher_h
 #define OffscreenCanvasFrameDispatcher_h
 
 #include "platform/PlatformExport.h"
+#include "platform/WebTaskRunner.h"
 #include "wtf/RefPtr.h"
 #include "wtf/WeakPtr.h"
 
 namespace blink {
 
 class StaticBitmapImage;
 
+class OffscreenCanvasFrameDispatcherClient {

[xlai (Olivia), 2016/12/21 19:54:25]

Just a suggestion: I see that the relationship of this new class to
OffscreenCanvasFrameDispatcher is similar to that
CanvasSurfaceLayerBridgeObserver to CanvasSurfaceLayerBridge. Do you think it's
better to rename "*Client" to "*Observer" for consistency or symmetry between
html canvas side and offscreencanvas side? 

[Justin Novosad, 2016/12/21 21:15:40]

We use both in blink. It is really just a matter of semantics.  The term
"Observer" implies that the object is watching another other (subscribing to
change notifications). The term "Client" implies that the object is being served
something (event signals, for example) by another object.  The difference is
subtle and it is the same code pattern. 

IMHO, both classes are aptly named as is.

+ public:
+  virtual void beginFrame() = 0;
+};
+
 class PLATFORM_EXPORT OffscreenCanvasFrameDispatcher {
  public:
-  OffscreenCanvasFrameDispatcher() : m_weakPtrFactory(this) {}
   virtual ~OffscreenCanvasFrameDispatcher() {}
   virtual void dispatchFrame(RefPtr<StaticBitmapImage>,
                              double commitStartTime,
-                             bool isWebGLSoftwareRendering = false) = 0;
+                             bool isWebGLSoftwareRendering) = 0;
   virtual void reclaimResource(unsigned resourceId) = 0;
 
   virtual void reshape(int width, int height) = 0;
 
   WeakPtr<OffscreenCanvasFrameDispatcher> createWeakPtr() {
     return m_weakPtrFactory.createWeakPtr();
   }
 
+  OffscreenCanvasFrameDispatcherClient* client() { return m_client; }
+
+ protected:
+  OffscreenCanvasFrameDispatcher(OffscreenCanvasFrameDispatcherClient* client)
+      : m_weakPtrFactory(this), m_client(client) {}
+
  private:
   WeakPtrFactory<OffscreenCanvasFrameDispatcher> m_weakPtrFactory;
+  OffscreenCanvasFrameDispatcherClient* m_client;
 };
 
 }  // namespace blink
 
 #endif  // OffscreenCanvasFrameDispatcher_h