ui: Cleanup class/struct forward declarations

ui/views/controls/menu/menu_runner.h

 // Copyright (c) 2012 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 UI_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_
 #define UI_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 14 matching lines @@
 }
 
 namespace ui {
 class MenuModel;
 }
 
 namespace views {
 
 class MenuButton;
 class MenuItemView;
-class MenuModelAdapter;
 class MenuRunnerHandler;
 class Widget;
 
 namespace internal {
 class DisplayChangeListener;
 class MenuRunnerImplInterface;
 }
 
 namespace test {
 class MenuRunnerTestAPI;
@@ skipping 128 matching lines @@
 
  protected:
   DisplayChangeListener() {}
 };
 
 }  // namespace internal
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_