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

examples/nfc_sender/nfc_sender.cc

Index: examples/nfc_sender/nfc_sender.cc
diff --git a/examples/nfc_sender/nfc_sender.cc b/examples/nfc_sender/nfc_sender.cc
index c2ed6a401dacdc61f2a0860742caa13d0d684116..cb705358b7bb45850824f4956cb97eb4f4cffd7a 100644
--- a/examples/nfc_sender/nfc_sender.cc
+++ b/examples/nfc_sender/nfc_sender.cc
@@ -204,8 +204,8 @@ class NfcSenderDelegate : public mojo::ApplicationDelegate,
   // mojo::ViewObserver
   void OnViewInputEvent(mojo::View* view,
                         const mojo::EventPtr& event) override {
-    if (event->action == mojo::EVENT_TYPE_POINTER_DOWN ||
-        event->action == mojo::EVENT_TYPE_POINTER_MOVE) {
+    if (event->action == mojo::EventType::POINTER_DOWN ||
+        event->action == mojo::EventType::POINTER_MOVE) {
       if (event->pointer_data) {
         gfx::Point point(event->pointer_data->x, event->pointer_data->y);