content: Cleanup class/struct forward declarations

content/public/renderer/plugin_instance_throttler.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_PUBLIC_RENDERER_PLUGIN_INSTANCE_THROTTLER_H_
 #define CONTENT_PUBLIC_RENDERER_PLUGIN_INSTANCE_THROTTLER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/common/content_export.h"
 #include "content/public/renderer/render_frame.h"
 
 namespace blink {
 class WebPlugin;
-struct WebPluginParams;
 }
 
 namespace gfx {
 class Size;
 }
 
 class SkBitmap;
 
 namespace content {
 
@@ skipping 77 matching lines @@
 
  protected:
   PluginInstanceThrottler() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PluginInstanceThrottler);
 };
 }
 
 #endif  // CONTENT_PUBLIC_RENDERER_PLUGIN_INSTANCE_THROTTLER_H_