[BackgroundSync] Use appopriate type parameters for WebCallbacks (2/4)

public/platform/modules/background_sync/WebSyncClient.h

 // Copyright 2015 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 WebSyncClient_h
 #define WebSyncClient_h
 
 #include "public/platform/WebCallbacks.h"
 #include "public/platform/modules/background_sync/WebSyncError.h"
+#include "public/platform/modules/background_sync/WebSyncProvider.h"
 
 namespace blink {
 
 class WebServiceWorkerRegistration;
 struct WebSyncRegistration;
 
-using WebSyncRegistrationCallbacks = WebCallbacks<WebSyncRegistration*, WebSyncError*>;
-
 class WebSyncClient {
 public:
     virtual ~WebSyncClient() { }
 
     // Ownership of the WebServiceWorkerRegistration is not transferred.
     // Ownership of the callbacks is transferred to the client.
     virtual void registerSync(WebServiceWorkerRegistration*, WebSyncRegistrationCallbacks*) = 0;
 };
 
 } // namespace blink
 
 #endif // WebSyncClient_h