Remove unused locks in mus ContextProvider classes

components/mus/surfaces/surfaces_context_provider.h

 // Copyright 2014 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 COMPONENTS_MUS_SURFACES_SURFACES_CONTEXT_PROVIDER_H_
 #define COMPONENTS_MUS_SURFACES_SURFACES_CONTEXT_PROVIDER_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/macros.h"
-#include "base/synchronization/lock.h"
 #include "base/threading/non_thread_safe.h"
 #include "cc/output/context_provider.h"
 #include "components/mus/gles2/command_buffer_local_client.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gl/gl_surface.h"
 
 namespace gpu {
 
 class TransferBuffer;
 
@@ skipping 55 matching lines @@
 
   gpu::Capabilities capabilities_;
   LostContextCallback lost_context_callback_;
 
   SurfacesContextProviderDelegate* delegate_;
   gfx::AcceleratedWidget widget_;
   CommandBufferLocal* command_buffer_local_;
 
   gfx::GLSurface::SwapCompletionCallback swap_buffers_completion_callback_;
 
-  base::Lock context_lock_;
-
   DISALLOW_COPY_AND_ASSIGN(SurfacesContextProvider);
 };
 
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_SURFACES_SURFACES_CONTEXT_PROVIDER_H_