[Sync] Replace uses of ObserverListThreadSafe with WeakHandles

chrome/browser/sync/internal_api/sync_manager.h

 // Copyright (c) 2011 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_SYNC_INTERNAL_API_SYNC_MANAGER_H_
 #define CHROME_BROWSER_SYNC_INTERNAL_API_SYNC_MANAGER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 478 matching lines @@
   // Switches the mode of operation to CONFIGURATION_MODE and
   // schedules a config task to fetch updates for |types|.
   void RequestConfig(const syncable::ModelTypeBitSet& types,
      sync_api::ConfigureReason reason);
 
   void RequestCleanupDisabledTypes();
 
   // Request a clearing of all data on the server
   void RequestClearServerData();
 
-  // Add/remove change observers.
-  void AddChangeObserver(ChangeObserver* observer);
-  void RemoveChangeObserver(ChangeObserver* observer);
-
   // Adds a listener to be notified of sync events.
   // NOTE: It is OK (in fact, it's probably a good idea) to call this before
   // having received OnInitializationCompleted.
   void AddObserver(Observer* observer);
 
   // Remove the given observer.  Make sure to call this if the
   // Observer is being destroyed so the SyncManager doesn't
   // potentially dereference garbage.
   void RemoveObserver(Observer* observer);
 
@@ skipping 88 matching lines @@
 syncable::ModelTypeSet GetTypesWithEmptyProgressMarkerToken(
     const syncable::ModelTypeSet types,
     sync_api::UserShare* share);
 
 // Returns the string representation of a PassphraseRequiredReason value.
 std::string PassphraseRequiredReasonToString(PassphraseRequiredReason reason);
 
 }  // namespace sync_api
 
 #endif  // CHROME_BROWSER_SYNC_INTERNAL_API_SYNC_MANAGER_H_