[Sync] Convert DTCs to be not RefCounted and NonThreadSafe.

components/sync_sessions/sessions_sync_manager.h

 // Copyright 2014 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 COMPONENTS_SYNC_SESSIONS_SESSIONS_SYNC_MANAGER_H_
 #define COMPONENTS_SYNC_SESSIONS_SESSIONS_SYNC_MANAGER_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 36 matching lines @@
 class SessionWindow;
 class TabNavigation;
 }  // namespace sync_pb
 
 namespace extensions {
 class ExtensionSessionsTest;
 }  // namespace extensions
 
 namespace browser_sync {
 
-class DataTypeErrorHandler;
 class SyncedTabDelegate;
 class SyncedWindowDelegatesGetter;
 
 // Contains all logic for associating the Chrome sessions model and
 // the sync sessions model.
 class SessionsSyncManager : public syncer::SyncableService,
                             public sync_driver::OpenTabsUIDelegate,
                             public LocalSessionEventHandler {
  public:
   SessionsSyncManager(sync_sessions::SyncSessionsClient* sessions_client,
@@ skipping 309 matching lines @@
 
   // Callback to inform sync that a sync data refresh is requested.
   base::Closure datatype_refresh_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionsSyncManager);
 };
 
 }  // namespace browser_sync
 
 #endif  // COMPONENTS_SYNC_SESSIONS_SESSIONS_SYNC_MANAGER_H_