[Sync] Update SyncBackendHost to forward ClearServerData to SyncManager

sync/internal_api/sync_manager_impl.cc

 // Copyright (c) 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.
 
 #include "sync/internal_api/sync_manager_impl.h"
 
 #include <string>
 
 #include "base/base64.h"
 #include "base/bind.h"
@@ skipping 1021 matching lines @@
 
 bool SyncManagerImpl::HasDirectoryTypeDebugInfoObserver(
     syncer::TypeDebugInfoObserver* observer) {
   return model_type_registry_->HasDirectoryTypeDebugInfoObserver(observer);
 }
 
 void SyncManagerImpl::RequestEmitDebugInfo() {
   model_type_registry_->RequestEmitDebugInfo();
 }
 
+void SyncManagerImpl::ClearServerData(const ClearServerDataCallback& callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  scheduler_->Start(SyncScheduler::CLEAR_SERVER_DATA_MODE, base::Time());
+  ClearParams params(callback);
+  scheduler_->ScheduleClearServerData(params);
+}
+
 }  // namespace syncer