chrome: Cleanup class/struct forward declarations

chrome/browser/chromeos/arc/arc_session_manager.h

 // Copyright 2016 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_CHROMEOS_ARC_ARC_SESSION_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_SESSION_MANAGER_H_
 
 #include <memory>
 #include <ostream>
 #include <string>
@@ skipping 22 matching lines @@
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 namespace arc {
 
 class ArcAndroidManagementChecker;
 class ArcAuthCodeFetcher;
 class ArcAuthContext;
 class ArcOptInPreferenceHandler;
-class ArcRobotAuth;
 enum class ProvisioningResult : int;
 
 // This class proxies the request from the client to fetch an auth code from
 // LSO. It lives on the UI thread.
 class ArcSessionManager : public ArcService,
                           public ArcBridgeService::Observer,
                           public ArcSupportHost::Observer,
                           public ArcOptInPreferenceHandlerObserver,
                           public sync_preferences::PrefServiceSyncableObserver,
                           public sync_preferences::SyncedPrefObserver {
@@ skipping 209 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(ArcSessionManager);
 };
 
 // Outputs the stringified |state| to |os|. This is only for logging purposes.
 std::ostream& operator<<(std::ostream& os,
                          const ArcSessionManager::State& state);
 
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_SESSION_MANAGER_H_