[Sync] Refactor sync manager into interface.

sync/internal_api/js_sync_manager_observer.cc

 // 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.
 
 #include "sync/internal_api/js_sync_manager_observer.h"
 
 #include <cstddef>
 
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/string_number_conversions.h"
 #include "base/values.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/internal_api/public/change_record.h"
 #include "sync/internal_api/public/sessions/sync_session_snapshot.h"
+#include "sync/internal_api/public/util/sync_string_conversions.h"
 #include "sync/js/js_arg_list.h"
 #include "sync/js/js_event_details.h"
 #include "sync/js/js_event_handler.h"
 #include "sync/sessions/session_state.h"
 
 namespace syncer {
 
 using syncer::SyncProtocolError;
 
 JsSyncManagerObserver::JsSyncManagerObserver() {}
@@ skipping 121 matching lines @@
     const std::string& name, const JsEventDetails& details) {
   if (!event_handler_.IsInitialized()) {
     NOTREACHED();
     return;
   }
   event_handler_.Call(from_here,
                       &JsEventHandler::HandleJsEvent, name, details);
 }
 
 }  // namespace syncer