[wrapper-tracing] WebGL and friends: Add write barriers

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

 /*
  * Copyright (C) 2004, 2006, 2007 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 107 matching lines @@
   return StaticBitmapImage::create(surface->makeImageSnapshot());
 }
 
 }  // namespace
 
 inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     : HTMLElement(canvasTag, document),
       ContextLifecycleObserver(&document),
       PageVisibilityObserver(document.page()),
       m_size(DefaultWidth, DefaultHeight),
+      m_context(this, nullptr),
       m_ignoreReset(false),
       m_externallyAllocatedMemory(0),
       m_originClean(true),
       m_didFailToCreateImageBuffer(false),
       m_imageBufferIsClear(false),
       m_numFramesSinceLastRenderingModeSwitch(0),
       m_pendingRenderingModeSwitch(false) {
   CanvasMetrics::countCanvasContextUsage(CanvasMetrics::CanvasCreated);
   UseCounter::count(document, UseCounter::HTMLCanvasElement);
 }
@@ skipping 1207 matching lines @@
   mojom::blink::OffscreenCanvasSurfacePtr service;
   Platform::current()->interfaceProvider()->getInterface(
       mojo::GetProxy(&service));
   m_surfaceLayerBridge =
       wrapUnique(new CanvasSurfaceLayerBridge(std::move(service)));
   return m_surfaceLayerBridge->createSurfaceLayer(this->width(),
                                                   this->height());
 }
 
 }  // namespace blink