[Sync] Replace ClearServerDataCallback with Closure.

components/sync/engine/sync_manager.h

 // Copyright 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 COMPONENTS_SYNC_ENGINE_SYNC_MANAGER_H_
 #define COMPONENTS_SYNC_ENGINE_SYNC_MANAGER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 251 matching lines @@
     // Carries shutdown requests across threads and will be used to cut short
     // any network I/O and tell the syncer to exit early.
     //
     // Must outlive SyncManager.
     CancelationSignal* cancelation_signal;
 
     // Optional nigori state to be restored.
     std::unique_ptr<SyncEncryptionHandler::NigoriState> saved_nigori_state;
   };
 
-  using ClearServerDataCallback = base::Callback<void(void)>;
-
   SyncManager();
   virtual ~SyncManager();
 
   // Initialize the sync manager using arguments from |args|.
   //
   // Note, args is passed by non-const pointer because it contains objects like
   // unique_ptr.
   virtual void Init(InitArgs* args) = 0;
 
   virtual ModelTypeSet InitialSyncEndedTypes() = 0;
@@ skipping 112 matching lines @@
 
   // Request that all current counter values be emitted as though they had just
   // been updated.  Useful for initializing new observers' state.
   virtual void RequestEmitDebugInfo() = 0;
 
   // Clears server data and invokes |callback| when complete.
   //
   // This is an asynchronous operation that requires interaction with the sync
   // server. The operation will automatically be retried with backoff until it
   // completes successfully or sync is shutdown.
-  virtual void ClearServerData(const ClearServerDataCallback& callback) = 0;
+  virtual void ClearServerData(const base::Closure& callback) = 0;
 
   // Updates Sync's tracking of whether the cookie jar has a mismatch with the
   // chrome account. See ClientConfigParams proto message for more info.
   // Note: this does not trigger a sync cycle. It just updates the sync context.
   virtual void OnCookieJarChanged(bool account_mismatch, bool empty_jar) = 0;
 
   // Adds memory usage statistics to |pmd| for chrome://tracing.
   virtual void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd) = 0;
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_SYNC_MANAGER_H_