content: Cleanup class/struct forward declarations

content/renderer/layout_test_dependencies.h

 // Copyright 2016 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 CONTENT_RENDER_LAYOUT_TEST_DEPENDENCIES_H_
 #define CONTENT_RENDER_LAYOUT_TEST_DEPENDENCIES_H_
 
 #include <stdint.h>
 #include <memory>
 
 #include "base/memory/ref_counted.h"
 
 namespace cc {
 class ContextProvider;
 class CopyOutputRequest;
 class CompositorFrameSink;
-class SharedBitmapManager;
 class SwapPromise;
 }
 
 namespace gpu {
 class GpuChannelHost;
 class GpuMemoryBufferManager;
 }
 
 namespace content {
 class CompositorDependencies;
@@ skipping 12 matching lines @@
 
   // Returns a SwapPromise which should be queued for the next compositor frame.
   virtual std::unique_ptr<cc::SwapPromise> RequestCopyOfOutput(
       int32_t routing_id,
       std::unique_ptr<cc::CopyOutputRequest> request) = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDER_LAYOUT_TEST_DEPENDENCIES_H_