ui: Cleanup class/struct forward declarations

ui/app_list/views/apps_grid_view_delegate.h

 // Copyright 2013 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_APP_LIST_VIEWS_APPS_GRID_VIEW_DELEGATE_H_
 #define UI_APP_LIST_VIEWS_APPS_GRID_VIEW_DELEGATE_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
 #include "ui/app_list/app_list_export.h"
 
-namespace base {
-class FilePath;
-}
-
 namespace app_list {
 
 class AppListItem;
 
 class APP_LIST_EXPORT AppsGridViewDelegate {
  public:
   // Invoked when an item is activated on the grid view. |event_flags| contains
   // the flags of the keyboard/mouse event that triggers the activation request.
   virtual void ActivateApp(AppListItem* item, int event_flags) = 0;
 
   // Called by the root grid view to cancel a drag that started inside a folder.
   // This can occur when the root grid is visible for a reparent and its model
   // changes, necessitating a cancel of the drag operation.
   virtual void CancelDragInActiveFolder() = 0;
 
  protected:
   virtual ~AppsGridViewDelegate() {}
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_VIEWS_APPS_GRID_VIEW_DELEGATE_H_