[Sync] Update SyncBackendHost to forward ClearServerData to SyncManager

sync/internal_api/sync_rollback_manager_base.h

 // Copyright 2014 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_INTERNAL_API_SYNC_ROLLBACK_MANAGER_BASE_H_
 #define SYNC_INTERNAL_API_SYNC_ROLLBACK_MANAGER_BASE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 52 matching lines @@
   UserShare* GetUserShare() override;
   const std::string cache_guid() override;
   bool ReceivedExperiment(Experiments* experiments) override;
   bool HasUnsyncedItems() override;
   SyncEncryptionHandler* GetEncryptionHandler() override;
   void RefreshTypes(ModelTypeSet types) override;
   SyncContextProxy* GetSyncContextProxy() override;
   ScopedVector<ProtocolEvent> GetBufferedProtocolEvents() override;
   scoped_ptr<base::ListValue> GetAllNodesForType(
       syncer::ModelType type) override;
+  void ClearServerData(const ClearServerDataCallback& callback) override;
 
   // DirectoryChangeDelegate implementation.
   void HandleTransactionCompleteChangeEvent(
       ModelTypeSet models_with_changes) override;
   ModelTypeSet HandleTransactionEndingChangeEvent(
       const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
       syncable::BaseTransaction* trans) override;
   void HandleCalculateChangesChangeEventFromSyncApi(
       const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
       syncable::BaseTransaction* trans,
@@ skipping 53 matching lines @@
   bool initialized_;
 
   base::WeakPtrFactory<SyncRollbackManagerBase> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncRollbackManagerBase);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_SYNC_ROLLBACK_MANAGER_BASE_H_