[mojo-bindings] Support reuse of native enum classes

mojo/public/tools/bindings/generators/mojom_cpp_generator.py

Index: mojo/public/tools/bindings/generators/mojom_cpp_generator.py
diff --git a/mojo/public/tools/bindings/generators/mojom_cpp_generator.py b/mojo/public/tools/bindings/generators/mojom_cpp_generator.py
index eb2f03bd20f8696fafb4df23f6822932421a9dd6..c40b428fd28de6982d5c85f98236a7be58f0e93a 100644
--- a/mojo/public/tools/bindings/generators/mojom_cpp_generator.py
+++ b/mojo/public/tools/bindings/generators/mojom_cpp_generator.py
@@ -168,7 +168,11 @@ def GetCppArrayArgWrapperType(kind):
 
 def GetCppResultWrapperType(kind):
   if IsTypemappedKind(kind):
-    return "const %s&" % GetNativeTypeName(kind)
+    if mojom.IsEnumKind(kind):
+      return GetNativeTypeName(kind)
+    else:
+      assert mojom.IsStructKind(kind)
+      return "const %s&" % GetNativeTypeName(kind)
   if mojom.IsEnumKind(kind):
     return GetNameForKind(kind)
   if mojom.IsStructKind(kind) or mojom.IsUnionKind(kind):
@@ -242,7 +246,11 @@ def GetCppWrapperType(kind):
 
 def GetCppConstWrapperType(kind):
   if IsTypemappedKind(kind):
-    return "const %s&" % GetNativeTypeName(kind)
+    if mojom.IsEnumKind(kind):
+      return GetNativeTypeName(kind)
+    else:
+      assert mojom.IsStructKind(kind)
+      return "const %s&" % GetNativeTypeName(kind)
   if mojom.IsStructKind(kind) or mojom.IsUnionKind(kind):
     return "%sPtr" % GetNameForKind(kind)
   if mojom.IsArrayKind(kind):