[Sync] Update SyncBackendHost to forward ClearServerData to SyncManager

sync/internal_api/sync_manager_impl.cc

Index: sync/internal_api/sync_manager_impl.cc
diff --git a/sync/internal_api/sync_manager_impl.cc b/sync/internal_api/sync_manager_impl.cc
index da6200288698200676604812693b5eb2e41ab324..67dd78f4c0d48b9390c5b9d21e7c2a27ab9254bd 100644
--- a/sync/internal_api/sync_manager_impl.cc
+++ b/sync/internal_api/sync_manager_impl.cc
@@ -1039,4 +1039,11 @@ 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