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

third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridgeTest.cpp

 /*
  * Copyright (C) 2011 Google Inc. 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.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 69 matching lines @@
     gpu::Capabilities getCapabilities()
     {
         return gpu::Capabilities();
     }
 
     gpu::gles2::GLES2Interface* contextGL() override
     {
         return m_gl;
     }
 
+    bool bindToCurrentThread() override { return false; }
+
     void setLostContextCallback(WebClosure) override {}
     void setErrorMessageCallback(WebFunction<void(const char*, int32_t id)>) {}
 
 private:
     gpu::gles2::GLES2Interface* m_gl;
     RefPtr<GrContext> m_grContext;
 };
 
 class Canvas2DLayerBridgePtr {
 public:
@@ skipping 941 matching lines @@
     WebExternalTextureMailbox mailbox;
     EXPECT_FALSE(bridge->prepareMailbox(&mailbox, 0));
     EXPECT_TRUE(bridge->checkSurfaceValid());
 
     // Tear down the bridge on the thread so that 'bridge' can go out of scope
     // without crashing due to thread checks
     postAndWaitDestroyBridgeTask(BLINK_FROM_HERE, testThread.get(), &bridge);
 }
 
 } // namespace blink