content: Cleanup class/struct forward declarations

content/renderer/input/render_widget_input_handler_delegate.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_RENDERER_INPUT_RENDER_WIDGET_INPUT_HANDLER_DELEGATE_H_
 #define CONTENT_RENDERER_INPUT_RENDER_WIDGET_INPUT_HANDLER_DELEGATE_H_
 
 #include <memory>
 
 #include "content/common/content_export.h"
 #include "content/common/input/input_event_ack.h"
 
 namespace blink {
 class WebGestureEvent;
 class WebMouseEvent;
-class WebMouseWheelEvent;
 }
 
 namespace gfx {
 class Point;
 class Vector2dF;
 }
 
 namespace content {
 
 class RenderWidgetInputHandler;
@@ skipping 62 matching lines @@
   // won't be sent to WebKit or trigger DidHandleMouseEvent().
   virtual bool WillHandleMouseEvent(const blink::WebMouseEvent& event) = 0;
 
  protected:
   virtual ~RenderWidgetInputHandlerDelegate() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_RENDER_WIDGET_INPUT_HANDLER_DELEGATE_H_