Synchronize OffscreenCanvas content with the placeholder canvas

third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h

 // Copyright 2015 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 OffscreenCanvas_h
 #define OffscreenCanvas_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/ScriptWrappable.h"
@@ skipping 29 matching lines @@
   void setWidth(unsigned, ExceptionState&);
   void setHeight(unsigned, ExceptionState&);
 
   // API Methods
   ImageBitmap* transferToImageBitmap(ScriptState*, ExceptionState&);
   ScriptPromise convertToBlob(ScriptState*,
                               const ImageEncodeOptions&,
                               ExceptionState&);
 
   IntSize size() const { return m_size; }
-  void setAssociatedCanvasId(int canvasId) { m_canvasId = canvasId; }
-  int getAssociatedCanvasId() const { return m_canvasId; }
+  void setPlaceholderCanvasId(int canvasId) {
+    m_placeholderCanvasId = canvasId;
+  }
+  int placeholderCanvasId() const { return m_placeholderCanvasId; }
+  bool hasPlaceholderCanvas() {
+    return m_placeholderCanvasId != kNoPlaceholderCanvas;
+  }
   bool isNeutered() const { return m_isNeutered; }
   void setNeutered();
   CanvasRenderingContext* getCanvasRenderingContext(
       ScriptState*,
       const String&,
       const CanvasContextCreationAttributes&);
   CanvasRenderingContext* renderingContext() { return m_context; }
 
   static void registerRenderingContextFactory(
       std::unique_ptr<CanvasRenderingContextFactory>);
@@ skipping 41 matching lines @@
 
  private:
   explicit OffscreenCanvas(const IntSize&);
 
   using ContextFactoryVector =
       Vector<std::unique_ptr<CanvasRenderingContextFactory>>;
   static ContextFactoryVector& renderingContextFactories();
   static CanvasRenderingContextFactory* getRenderingContextFactory(int);
 
   Member<CanvasRenderingContext> m_context;
-  int m_canvasId = -1;  // DOMNodeIds starts from 0, using -1 to indicate no
-                        // associated canvas element.
+
+  enum {
+    kNoPlaceholderCanvas = -1,  // DOMNodeIds starts from 0, using -1 to
+                                // indicate no associated canvas element.
+  };
+  int m_placeholderCanvasId = kNoPlaceholderCanvas;
 
   IntSize m_size;
   bool m_isNeutered = false;
 
   bool m_originClean;
   bool m_disableReadingFromCanvas = false;
 
   bool isPaintable() const;
 
   std::unique_ptr<OffscreenCanvasFrameDispatcher> m_frameDispatcher;
   // cc::SurfaceId is broken into three integer components as this can be used
   // in transfer of OffscreenCanvas across threads
   // If this object is not created via
   // HTMLCanvasElement.transferControlToOffscreen(),
   // then the following members would remain as initialized zero values.
   uint32_t m_clientId = 0;
   uint32_t m_sinkId = 0;
   uint32_t m_localId = 0;
   uint64_t m_nonceHigh = 0;
   uint64_t m_nonceLow = 0;
 };
 
 }  // namespace blink
 
 #endif  // OffscreenCanvas_h