(not for commit) Simplified multi-threaded Ganesh with lock on Flush only.

cc/output/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_OUTPUT_CONTEXT_PROVIDER_H_
 #define CC_OUTPUT_CONTEXT_PROVIDER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
 #include "cc/base/cc_export.h"
 #include "gpu/command_buffer/common/capabilities.h"
 
 class GrContext;
 
 namespace gpu {
 class ContextSupport;
 namespace gles2 { class GLES2Interface; }
 }
 
 namespace cc {
 struct ManagedMemoryPolicy;
 
 class ContextProvider : public base::RefCountedThreadSafe<ContextProvider> {
  public:
   // Bind the 3d context to the current thread. This should be called before
   // accessing the contexts. Calling it more than once should have no effect.
   // Once this function has been called, the class should only be accessed
   // from the same thread.
   virtual bool BindToCurrentThread() = 0;
+  virtual void RebindToCurrentThread() {}
 
   virtual gpu::gles2::GLES2Interface* ContextGL() = 0;
   virtual gpu::ContextSupport* ContextSupport() = 0;
   virtual class GrContext* GrContext() = 0;
 
   struct Capabilities {
     gpu::Capabilities gpu;
     size_t max_transfer_buffer_usage_bytes;
 
     CC_EXPORT Capabilities();
@@ skipping 33 matching lines @@
       const MemoryPolicyChangedCallback& memory_policy_changed_callback) = 0;
 
  protected:
   friend class base::RefCountedThreadSafe<ContextProvider>;
   virtual ~ContextProvider() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_CONTEXT_PROVIDER_H_