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

services/native_viewport/native_viewport_impl.cc

Index: services/native_viewport/native_viewport_impl.cc
diff --git a/services/native_viewport/native_viewport_impl.cc b/services/native_viewport/native_viewport_impl.cc
index ce258332a8acf7acecf63e12da964b1bd735fb9a..6b8658687e9ae51705c388c72ac84c8e8360a74e 100644
--- a/services/native_viewport/native_viewport_impl.cc
+++ b/services/native_viewport/native_viewport_impl.cc
@@ -128,7 +128,7 @@ bool NativeViewportImpl::OnEvent(mojo::EventPtr event) {
 
   mojo::NativeViewportEventDispatcher::OnEventCallback callback;
   switch (event->action) {
-    case mojo::EVENT_TYPE_POINTER_MOVE: {
+    case mojo::EventType::POINTER_MOVE: {
       // TODO(sky): add logic to remember last event location and not send if
       // the same.
       if (pointers_waiting_on_ack_.count(event->pointer_data->pointer_id))
@@ -141,11 +141,11 @@ bool NativeViewportImpl::OnEvent(mojo::EventPtr event) {
       break;
     }
 
-    case mojo::EVENT_TYPE_POINTER_CANCEL:
+    case mojo::EventType::POINTER_CANCEL:
       pointers_waiting_on_ack_.clear();
       break;
 
-    case mojo::EVENT_TYPE_POINTER_UP:
+    case mojo::EventType::POINTER_UP:
       pointers_waiting_on_ack_.erase(event->pointer_data->pointer_id);
       break;