[Sync] Remove unneeded 'using syncer::' lines and 'syncer::' scopings

sync/notifier/sync_notifier_observer.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 SYNC_NOTIFIER_SYNC_NOTIFIER_OBSERVER_H_
 #define SYNC_NOTIFIER_SYNC_NOTIFIER_OBSERVER_H_
 
 #include "sync/internal_api/public/base/model_type_payload_map.h"
 #include "sync/notifier/notifications_disabled_reason.h"
 
@@ skipping 12 matching lines @@
   virtual void OnNotificationsEnabled() = 0;
 
   // Called when notifications are disabled, with the reason in
   // |reason|.
   virtual void OnNotificationsDisabled(
       NotificationsDisabledReason reason) = 0;
 
   // Called when a notification is received.  The per-type payloads
   // are in |type_payloads| and the source is in |source|.
   virtual void OnIncomingNotification(
-      const syncer::ModelTypePayloadMap& type_payloads,
+      const ModelTypePayloadMap& type_payloads,
       IncomingNotificationSource source) = 0;
 
  protected:
   virtual ~SyncNotifierObserver() {}
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_NOTIFIER_SYNC_NOTIFIER_OBSERVER_H_