cc: Implement shared worker contexts.

content/common/gpu/client/context_provider_command_buffer.h

Index: content/common/gpu/client/context_provider_command_buffer.h
diff --git a/content/common/gpu/client/context_provider_command_buffer.h b/content/common/gpu/client/context_provider_command_buffer.h
index 1e0d23f82b915609416ce8473e6d4f83d6fd24bb..8a886a0cb65348b36f38bfa6ecbeb4b8b5fad975 100644
--- a/content/common/gpu/client/context_provider_command_buffer.h
+++ b/content/common/gpu/client/context_provider_command_buffer.h
@@ -30,6 +30,14 @@ class CONTENT_EXPORT ContextProviderCommandBuffer
 
   CommandBufferProxyImpl* GetCommandBufferProxy();
 
+  // Force the command buffer to be torn down as if the context was lost. The
+  // context can still be used just like in lost context situations but it is
+  // no longer bound to a specific thread so it is safe for the previously
+  // bound thread to drop any reference it has. This should only be used if
+  // content provider has been set up for multi-threaded usage by calling
+  // SetupLock().
+  void Destroy();
+
   // cc_blink::ContextProviderWebContext implementation.
   WebGraphicsContext3DCommandBufferImpl* WebContext3D() override;
 
@@ -63,6 +71,7 @@ class CONTENT_EXPORT ContextProviderCommandBuffer
 
  private:
   void InitializeCapabilities();
+  void DestroyWithMainThreadLockAcquired();
 
   base::ThreadChecker main_thread_checker_;
   base::ThreadChecker context_thread_checker_;