[mojo-bindings] Support reuse of native enum classes

mojo/public/tools/bindings/pylib/mojom/parse/parser.py

Index: mojo/public/tools/bindings/pylib/mojom/parse/parser.py
diff --git a/mojo/public/tools/bindings/pylib/mojom/parse/parser.py b/mojo/public/tools/bindings/pylib/mojom/parse/parser.py
index 8d90cd5da049e9045b0832adb22df9f4b54141d7..772d254cabba720a4ad110e7381a08df41911c33 100644
--- a/mojo/public/tools/bindings/pylib/mojom/parse/parser.py
+++ b/mojo/public/tools/bindings/pylib/mojom/parse/parser.py
@@ -334,7 +334,7 @@ class Parser(object):
                        snippet=self._GetSnippet(p.lineno(1)))
     p[0] = ast.Ordinal(value, filename=self.filename, lineno=p.lineno(1))
 
-  def p_enum(self, p):
+  def p_enum_1(self, p):
     """enum : attribute_section ENUM NAME LBRACE nonempty_enum_value_list \
                   RBRACE SEMI
             | attribute_section ENUM NAME LBRACE nonempty_enum_value_list \
@@ -342,6 +342,11 @@ class Parser(object):
     p[0] = ast.Enum(p[3], p[1], p[5], filename=self.filename,
                     lineno=p.lineno(2))
 
+  def p_enum_2(self, p):
+    """enum : attribute_section ENUM NAME SEMI"""
+    p[0] = ast.Enum(p[3], p[1], None, filename=self.filename,
+                    lineno=p.lineno(2))
+
   def p_nonempty_enum_value_list_1(self, p):
     """nonempty_enum_value_list : enum_value"""
     p[0] = ast.EnumValueList(p[1])