content: Cleanup class/struct forward declarations

content/browser/renderer_host/render_widget_host_view_mus.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_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MUS_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MUS_H_
 
 #include <stddef.h>
 
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "content/browser/renderer_host/render_widget_host_view_base.h"
 #include "content/public/browser/render_process_host_observer.h"
 #include "services/ui/public/cpp/input_event_handler.h"
 #include "services/ui/public/cpp/scoped_window_ptr.h"
 #include "services/ui/public/cpp/window.h"
 
 namespace content {
 
 class RenderWidgetHost;
 class RenderWidgetHostImpl;
-struct NativeWebKeyboardEvent;
 struct TextInputState;
 
 // See comments in render_widget_host_view.h about this class and its members.
 // This version of RenderWidgetHostView is for builds of Chrome that run through
 // the standalone service runner and use the Mandoline UI Service (Mus). Mus is
 // responsible for windowing, compositing, and input event dispatch. The purpose
 // of RenderWidgetHostViewMus is to manage the ui::Window owned by the content
 // embedder. The browser is the owner of the ui::Window, controlling properties
 // such as visibility, and bounds. Some aspects such as input, focus, and cursor
 // are managed by Mus directly. Input event routing will be plumbed directly to
@@ skipping 96 matching lines @@
   aura::Window* aura_window_;
 
   std::unique_ptr<ui::ScopedWindowPtr> mus_window_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewMus);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MUS_H_