content: Cleanup class/struct forward declarations

content/browser/renderer_host/render_widget_host_view_event_handler.h

 // Copyright 2016 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_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_EVENT_HANDLER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_EVENT_HANDLER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 15 matching lines @@
 }  // namespace blink
 
 namespace ui {
 class TextInputClient;
 class TouchSelectionController;
 }
 
 namespace content {
 struct ContextMenuParams;
 class OverscrollController;
-class RenderViewHost;
 class RenderWidgetHostImpl;
 class RenderWidgetHostViewBase;
 class TouchSelectionControllerClientAura;
 
 // Provides an implementation of ui::EventHandler for use with
 // RenderWidgetHostViewBase. A delegate is required in order to provide platform
 // specific functionality.
 //
 // After processing events they will be forwarded to the provided
 // RenderWidgetHostImpl.
@@ skipping 197 matching lines @@
   ui::EventHandler* popup_child_event_handler_;
   Delegate* const delegate_;
   aura::Window* window_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewEventHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_EVENT_HANDLER_H_