Remove calls to deprecated MessageLoop methods in components.

components/sync_driver/glue/sync_backend_host_impl.cc

Index: components/sync_driver/glue/sync_backend_host_impl.cc
diff --git a/components/sync_driver/glue/sync_backend_host_impl.cc b/components/sync_driver/glue/sync_backend_host_impl.cc
index bbe94286550f9315834d8874ba3d6955fca2fc1f..7f75372a47fb54acce7dae5c3c4bcebd01cc53e9 100644
--- a/components/sync_driver/glue/sync_backend_host_impl.cc
+++ b/components/sync_driver/glue/sync_backend_host_impl.cc
@@ -495,8 +495,8 @@ void SyncBackendHostImpl::GetModelSafeRoutingInfo(
 
 void SyncBackendHostImpl::FlushDirectory() const {
   DCHECK(initialized());
-  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
-      base::Bind(&SyncBackendHostCore::SaveChanges, core_));
+  registrar_->sync_thread()->task_runner()->PostTask(
+      FROM_HERE, base::Bind(&SyncBackendHostCore::SaveChanges, core_));
 }
 
 void SyncBackendHostImpl::RequestBufferedProtocolEventsAndEnableForwarding() {