Implement offscreenCanvas.getContext('webgl') on a worker thread

content/renderer/renderer_blink_platform_impl.h

 // Copyright (c) 2012 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 CONTENT_RENDERER_RENDERER_BLINK_PLATFORM_IMPL_H_
 #define CONTENT_RENDERER_RENDERER_BLINK_PLATFORM_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 158 matching lines @@
       double frame_rate,
       blink::WebMediaStreamTrack* track) override;
   void createHTMLVideoElementCapturer(
       blink::WebMediaStream* web_media_stream,
       blink::WebMediaPlayer* web_media_player) override;
   blink::WebImageCaptureFrameGrabber* createImageCaptureFrameGrabber() override;
   blink::WebGraphicsContext3DProvider* createOffscreenGraphicsContext3DProvider(
       const blink::Platform::ContextAttributes& attributes,
       const blink::WebURL& top_document_web_url,
       blink::WebGraphicsContext3DProvider* share_provider,
-      blink::Platform::GraphicsInfo* gl_info) override;
+      blink::Platform::GraphicsInfo* gl_info,
+      blink::Platform::WillBindToCurrentThread) override;
   blink::WebGraphicsContext3DProvider*
   createSharedOffscreenGraphicsContext3DProvider() override;
   blink::WebCompositorSupport* compositorSupport() override;
   blink::WebString convertIDNToUnicode(const blink::WebString& host) override;
   blink::ServiceRegistry* serviceRegistry() override;
   void startListening(blink::WebPlatformEventType,
                       blink::WebPlatformEventListener*) override;
   void stopListening(blink::WebPlatformEventType) override;
   void queryStorageUsageAndQuota(const blink::WebURL& storage_partition,
                                  blink::WebStorageQuotaType,
@@ skipping 114 matching lines @@
   std::unique_ptr<LocalStorageCachedAreas> local_storage_cached_areas_;
 
   std::unique_ptr<BlinkServiceRegistryImpl> blink_service_registry_;
 
   DISALLOW_COPY_AND_ASSIGN(RendererBlinkPlatformImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDERER_BLINK_PLATFORM_IMPL_H_