chrome: Cleanup class/struct forward declarations

chrome/browser/ui/hung_plugin_tab_helper.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 CHROME_BROWSER_UI_HUNG_PLUGIN_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_HUNG_PLUGIN_TAB_HELPER_H_
 
 #include <map>
 
 #include "base/macros.h"
 #include "base/memory/linked_ptr.h"
 #include "base/strings/string16.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace base {
 class FilePath;
 }
 
-namespace infobars {
-class InfoBarDelegate;
-}
-
 // Manages per-tab state with regard to hung plugins. This only handles
 // Pepper plugins which we know are windowless. Hung NPAPI plugins (which
 // may have native windows) can not be handled with infobars and have a
 // separate OS-specific hang monitoring.
 //
 // Our job is:
 // - Pop up an infobar when a plugin is hung.
 // - Terminate the plugin process if the user so chooses.
 // - Periodically re-show the hung plugin infobar if the user closes it without
 //   terminating the plugin.
@@ skipping 42 matching lines @@
 
   content::NotificationRegistrar registrar_;
 
   // All currently hung plugins.
   PluginStateMap hung_plugins_;
 
   DISALLOW_COPY_AND_ASSIGN(HungPluginTabHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_HUNG_PLUGIN_TAB_HELPER_H_