Notify listeners on OffScreenCanvas changes

third_party/WebKit/Source/core/html/HTMLCanvasElement.h

 /*
  * Copyright (C) 2004, 2006, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 191 matching lines @@
   void doDeferredPaintInvalidation();
 
   // ImageBitmapSource implementation
   IntSize bitmapSourceSize() const override;
   ScriptPromise createImageBitmap(ScriptState*,
                                   EventTarget&,
                                   Optional<IntRect> cropRect,
                                   const ImageBitmapOptions&,
                                   ExceptionState&) override;
 
+  // OffscreenCanvasPlaceholder implementation.
+  void setPlaceholderFrame(RefPtr<StaticBitmapImage>,
+                           WeakPtr<OffscreenCanvasFrameDispatcher>,
+                           RefPtr<WebTaskRunner>,
+                           unsigned resourceId) override;
   DECLARE_VIRTUAL_TRACE();
 
   DECLARE_VIRTUAL_TRACE_WRAPPERS();
 
   void createImageBufferUsingSurfaceForTesting(
       std::unique_ptr<ImageBufferSurface>);
 
   static void registerRenderingContextFactory(
       std::unique_ptr<CanvasRenderingContextFactory>);
   void updateExternallyAllocatedMemory() const;
@@ skipping 90 matching lines @@
   // Used for OffscreenCanvas that controls this HTML canvas element
   std::unique_ptr<CanvasSurfaceLayerBridge> m_surfaceLayerBridge;
 
   int m_numFramesSinceLastRenderingModeSwitch;
   bool m_pendingRenderingModeSwitch;
 };
 
 }  // namespace blink
 
 #endif  // HTMLCanvasElement_h