Add support for empty parameter lists.

mojo/public/bindings/parser/mojo_parser.py

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Generates a syntax tree from a Mojo IDL file."""
 
 
 import sys
 import os.path
@@ skipping 167 matching lines @@
       p[0] = ListFromConcat(p[1], p[2])
 
   def p_method(self, p):
     """method : VOID NAME LPAREN parameters RPAREN ordinal SEMICOLON"""
     p[0] = ('METHOD', p[2], p[4], p[6])
 
   def p_parameters(self, p):
     """parameters : parameter
                   | parameter COMMA parameters
                   | """
-    if len(p) == 2:
-      p[0] = p[1]
+    if len(p) == 1:
+      p[0] = []
+    elif len(p) == 2:
+      p[0] = ListFromConcat(p[1])
     elif len(p) > 3:
       p[0] = ListFromConcat(p[1], p[3])
 
   def p_parameter(self, p):
     """parameter : typename NAME ordinal"""
     p[0] = ('PARAM', p[1], p[2], p[3])
 
   def p_typename(self, p):
     """typename : NAME
                 | ARRAY"""
@@ skipping 23 matching lines @@
 def Main():
   if len(sys.argv) < 2:
     print("usage: %s filename" % (sys.argv[0]))
     sys.exit(1)
   tree = Parse(filename=sys.argv[1])
   print(tree)
 
 
 if __name__ == '__main__':
   Main()