content: Cleanup class/struct forward declarations

content/shell/browser/shell_platform_data_aura.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 CONTENT_SHELL_BROWSER_SHELL_PLATFORM_DATA_AURA_H_
 #define CONTENT_SHELL_BROWSER_SHELL_PLATFORM_DATA_AURA_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/aura/window_tree_host.h"
 
 namespace aura {
 namespace client {
 class DefaultCaptureClient;
 class FocusClient;
 class WindowParentingClient;
 }
 }
 
 namespace gfx {
 class Size;
 }
 
-namespace ui {
-class EventHandler;
-}
-
 namespace content {
 
 class ShellPlatformDataAura {
  public:
   explicit ShellPlatformDataAura(const gfx::Size& initial_size);
   ~ShellPlatformDataAura();
 
   void ShowWindow();
   void ResizeWindow(const gfx::Size& size);
 
   aura::WindowTreeHost* host() { return host_.get(); }
 
  private:
   std::unique_ptr<aura::WindowTreeHost> host_;
   std::unique_ptr<aura::client::FocusClient> focus_client_;
   std::unique_ptr<aura::client::DefaultCaptureClient> capture_client_;
   std::unique_ptr<aura::client::WindowParentingClient> window_parenting_client_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellPlatformDataAura);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_SHELL_BROWSER_SHELL_PLATFORM_DATA_AURA_H_