chrome: Cleanup class/struct forward declarations

chrome/browser/plugins/plugin_installer.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_PLUGINS_PLUGIN_INSTALLER_H_
 #define CHROME_BROWSER_PLUGINS_PLUGIN_INSTALLER_H_
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "base/strings/string16.h"
 #include "base/version.h"
 #include "chrome/browser/plugins/plugin_metadata.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 #include "content/public/browser/download_item.h"
 #include "url/gurl.h"
 
 class PluginInstallerObserver;
 class WeakPluginInstallerObserver;
 
 namespace content {
 class DownloadManager;
 class WebContents;
-struct WebPluginInfo;
 }
 
 class PluginInstaller : public content::DownloadItem::Observer {
  public:
   enum InstallerState {
     INSTALLER_STATE_IDLE,
     INSTALLER_STATE_DOWNLOADING,
   };
 
   PluginInstaller();
@@ skipping 35 matching lines @@
   base::ObserverList<WeakPluginInstallerObserver> weak_observers_;
 
   FRIEND_TEST_ALL_PREFIXES(PluginInstallerTest,
                            StartInstalling_SuccessfulDownload);
   FRIEND_TEST_ALL_PREFIXES(PluginInstallerTest, StartInstalling_FailedStart);
   FRIEND_TEST_ALL_PREFIXES(PluginInstallerTest, StartInstalling_Interrupted);
   DISALLOW_COPY_AND_ASSIGN(PluginInstaller);
 };
 
 #endif  // CHROME_BROWSER_PLUGINS_PLUGIN_INSTALLER_H_