Synchronize OffscreenCanvas content with the placeholder canvas

third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.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 "modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.h"
 
 #include "bindings/modules/v8/OffscreenCanvasRenderingContext2DOrWebGLRenderingContextOrWebGL2RenderingContext.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/frame/Settings.h"
 #include "core/workers/WorkerGlobalScope.h"
@@ skipping 31 matching lines @@
 
 DEFINE_TRACE(OffscreenCanvasRenderingContext2D) {
   CanvasRenderingContext::trace(visitor);
   BaseRenderingContext2D::trace(visitor);
 }
 
 void OffscreenCanvasRenderingContext2D::commit(ScriptState* scriptState,
                                                ExceptionState& exceptionState) {
   UseCounter::Feature feature = UseCounter::OffscreenCanvasCommit2D;
   UseCounter::count(scriptState->getExecutionContext(), feature);
-  if (getOffscreenCanvas()->getAssociatedCanvasId() < 0) {
+  if (!getOffscreenCanvas()->hasPlaceholderCanvas()) {
     // If an OffscreenCanvas has no associated canvas Id, it indicates that
     // it is not an OffscreenCanvas created by transfering control from html
     // canvas.
     exceptionState.throwDOMException(InvalidStateError,
                                      "Commit() was called on a context whose "
                                      "OffscreenCanvas is not associated with a "
                                      "canvas element.");
     return;
   }
   double commitStartTime = WTF::monotonicallyIncreasingTime();
@@ skipping 178 matching lines @@
 }
 
 bool OffscreenCanvasRenderingContext2D::isContextLost() const {
   return false;
 }
 
 bool OffscreenCanvasRenderingContext2D::isPaintable() const {
   return this->imageBuffer();
 }
 }