[background-sync] Remove WebSyncError and SyncCallbacks

third_party/WebKit/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"
-
-namespace blink {
-
-class WebServiceWorkerRegistration;
-struct WebSyncRegistration;
-
-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