content: Cleanup class/struct forward declarations

content/renderer/mus/render_widget_mus_connection.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 CONTENT_RENDERER_MUS_RENDER_WIDGET_MUS_CONNECTION_H_
 #define CONTENT_RENDERER_MUS_RENDER_WIDGET_MUS_CONNECTION_H_
 
 #include "base/macros.h"
 #include "base/threading/thread_checker.h"
 #include "cc/output/compositor_frame_sink.h"
 #include "content/common/content_export.h"
 #include "content/renderer/input/render_widget_input_handler_delegate.h"
 #include "content/renderer/mus/compositor_mus_connection.h"
 
 namespace gpu {
 class GpuChannelHost;
 class GpuMemoryBufferManager;
 }
 
 namespace content {
 
-class InputHandlerManager;
-
 // Use on main thread.
 class CONTENT_EXPORT RenderWidgetMusConnection
     : public RenderWidgetInputHandlerDelegate {
  public:
   // Bind to a WindowTreeClient request.
   void Bind(mojo::InterfaceRequest<ui::mojom::WindowTreeClient> request);
 
   // Create a cc output surface.
   std::unique_ptr<cc::CompositorFrameSink> CreateCompositorFrameSink(
       scoped_refptr<gpu::GpuChannelHost> gpu_channel_host,
@@ skipping 44 matching lines @@
 
   // Used to verify single threaded access.
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetMusConnection);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MUS_RENDER_WIDGET_MUS_CONNECTION_H_