Revert of Deletes mojo::Callback

content/renderer/background_sync/background_sync_client_impl.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 CONTENT_RENDERER_BACKGROUND_SYNC_BACKGROUND_SYNC_CLIENT_IMPL_H_
 #define CONTENT_RENDERER_BACKGROUND_SYNC_BACKGROUND_SYNC_CLIENT_IMPL_H_
 
 #include <stdint.h>
 
 #include <map>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/common/content_export.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "third_party/WebKit/public/platform/modules/background_sync/background_sync.mojom.h"
 
 namespace content {
 
 class CONTENT_EXPORT BackgroundSyncClientImpl
     : public NON_EXPORTED_BASE(blink::mojom::BackgroundSyncServiceClient) {
  public:
   static void Create(mojo::InterfaceRequest<
                      blink::mojom::BackgroundSyncServiceClient> request);
 
   ~BackgroundSyncClientImpl() override;
 
  private:
+  using SyncCallback =
+      mojo::Callback<void(blink::mojom::ServiceWorkerEventStatus)>;
   explicit BackgroundSyncClientImpl(
       mojo::InterfaceRequest<blink::mojom::BackgroundSyncServiceClient>
           request);
 
   // BackgroundSyncServiceClient methods:
   void Sync(const mojo::String& tag,
             blink::mojom::BackgroundSyncEventLastChance last_chance,
             const SyncCallback& callback) override;
 
   mojo::StrongBinding<blink::mojom::BackgroundSyncServiceClient> binding_;
 
   DISALLOW_COPY_AND_ASSIGN(BackgroundSyncClientImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_BACKGROUND_SYNC_BACKGROUND_SYNC_CLIENT_IMPL_H_