For c++, Generate enum classes instead of enum from mojom.

mojo/services/view_manager/public/cpp/lib/view_manager_client_impl.cc

Index: mojo/services/view_manager/public/cpp/lib/view_manager_client_impl.cc
diff --git a/mojo/services/view_manager/public/cpp/lib/view_manager_client_impl.cc b/mojo/services/view_manager/public/cpp/lib/view_manager_client_impl.cc
index 52d1b48c5d6581af47a8e65118045592fac5bb09..b8262d1a95a8c5277fea0ceb001ec3b233662369 100644
--- a/mojo/services/view_manager/public/cpp/lib/view_manager_client_impl.cc
+++ b/mojo/services/view_manager/public/cpp/lib/view_manager_client_impl.cc
@@ -242,7 +242,7 @@ Id ViewManagerClientImpl::CreateViewOnServer() {
   DCHECK(service_);
   const Id view_id = MakeTransportId(connection_id_, ++next_id_);
   service_->CreateView(view_id, [this](ErrorCode code) {
-    OnActionCompleted(code == ERROR_CODE_NONE);
+    OnActionCompleted(code == ErrorCode::NONE);
   });
   return view_id;
 }