ui: Cleanup class/struct forward declarations

ui/events/event_handler.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_EVENTS_EVENT_HANDLER_H_
 #define UI_EVENTS_EVENT_HANDLER_H_
 
 #include <stack>
 #include <vector>
 
 #include "base/macros.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/events_export.h"
 
 namespace ui {
 
 class CancelModeEvent;
 class Event;
 class EventDispatcher;
-class EventTarget;
 class GestureEvent;
 class KeyEvent;
 class MouseEvent;
 class ScrollEvent;
 class TouchEvent;
 
 // Dispatches events to appropriate targets.  The default implementations of
 // all of the specific handlers (e.g. OnKeyEvent, OnMouseEvent) do nothing.
 class EVENTS_EXPORT EventHandler {
  public:
@@ skipping 26 matching lines @@
   std::stack<EventDispatcher*> dispatchers_;
 
   DISALLOW_COPY_AND_ASSIGN(EventHandler);
 };
 
 typedef std::vector<EventHandler*> EventHandlerList;
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_HANDLER_H_