Provide shared context to Platform API in renderer.

cc/context_provider.h

 // Copyright (c) 2013 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 CC_CONTEXT_PROVIDER_H_
 #define CC_CONTEXT_PROVIDER_H_
 
 #include "base/memory/ref_counted.h"
 
 class GrContext;
@@ skipping 14 matching lines @@
   virtual bool BindToCurrentThread() = 0;
 
   virtual WebKit::WebGraphicsContext3D* Context3d() = 0;
   virtual class GrContext* GrContext() = 0;
 
   // Ask the provider to check if the contexts are valid or lost. If they are,
   // this should invalidate the provider so that it can be replaced with a new
   // one.
   virtual void VerifyContexts() = 0;
 
+  // A method to be called from the main thread that should return true if
+  // the context inside the provider is no longer valid.
+  virtual bool DestroyedOnMainThread() = 0;
+
  protected:
   friend class base::RefCountedThreadSafe<ContextProvider>;
   virtual ~ContextProvider() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_CONTEXT_PROVIDER_H_