components: Cleanup class/struct fwd declarations

components/exo/buffer.h

 // Copyright 2015 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_EXO_BUFFER_H_
 #define COMPONENTS_EXO_BUFFER_H_
 
 #include <memory>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace base {
 namespace trace_event {
 class TracedValue;
 }
 }
 
 namespace cc {
 class SingleReleaseCallback;
 class TextureMailbox;
 }
 
 namespace gfx {
 class GpuMemoryBuffer;
 }
 
-namespace gpu {
-struct SyncToken;
-}
-
 namespace exo {
 
 // This class provides the content for a Surface. The mechanism by which a
 // client provides and updates the contents is the responsibility of the client
 // and not defined as part of this class.
 class Buffer : public base::SupportsWeakPtr<Buffer> {
  public:
   explicit Buffer(std::unique_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer);
   Buffer(std::unique_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer,
          unsigned texture_target,
@@ skipping 82 matching lines @@
 
   // The client release callback.
   base::Closure release_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(Buffer);
 };
 
 }  // namespace exo
 
 #endif  // COMPONENTS_EXO_BUFFER_H_