chrome: Cleanup class/struct forward declarations

chrome/renderer/plugins/plugin_preroller.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 CHROME_RENDERER_PLUGINS_PLUGIN_PREROLLER_H_
 #define CHROME_RENDERER_PLUGINS_PLUGIN_PREROLLER_H_
 
 #include "base/macros.h"
 #include "content/public/common/webplugininfo.h"
 #include "content/public/renderer/plugin_instance_throttler.h"
 #include "content/public/renderer/render_frame_observer.h"
 #include "third_party/WebKit/public/web/WebPluginParams.h"
 #include "url/gurl.h"
 
 namespace blink {
 class WebLocalFrame;
-class WebPlugin;
 }
 
 class SkBitmap;
 
 // This class manages a plugin briefly for the purposes of keyframe extraction.
 // Once a keyframe has been extracted, this class will replace the plugin with
 // a ChromePluginPlaceholder. The actual plugin will continue to live in a
 // throttled state. This class manages its own lifetime.
 class PluginPreroller : public content::PluginInstanceThrottler::Observer,
                         public content::RenderFrameObserver {
@@ skipping 27 matching lines @@
   base::string16 message_;
 
   content::PluginInstanceThrottler* throttler_;
 
   GURL keyframe_data_url_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginPreroller);
 };
 
 #endif  // CHROME_RENDERER_PLUGINS_PLUGIN_PREROLLER_H_