chrome: Cleanup class/struct forward declarations

chrome/installer/util/google_update_settings.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_INSTALLER_UTIL_GOOGLE_UPDATE_SETTINGS_H_
 #define CHROME_INSTALLER_UTIL_GOOGLE_UPDATE_SETTINGS_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "base/time/time.h"
 #include "base/version.h"
 #include "build/build_config.h"
 #include "chrome/installer/util/util_constants.h"
 #include "components/metrics/client_info.h"
 
-class AppRegistrationData;
 class BrowserDistribution;
 
 namespace installer {
 class ChannelInfo;
 class InstallationState;
 }
 
 // This class provides accessors to the Google Update group policies and
 // 'ClientState' information. The group policies are set using specific
 // administrative templates. The 'ClientState' information is recorded when the
@@ skipping 309 matching lines @@
   // this will do nothing to |experiment_labels|. This will return true if the
   // label did not exist, or was successfully read.
   static bool ReadExperimentLabels(bool system_install,
                                    base::string16* experiment_labels);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(GoogleUpdateSettings);
 };
 
 #endif  // CHROME_INSTALLER_UTIL_GOOGLE_UPDATE_SETTINGS_H_