Support nullable types in mojom.

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

 # Copyright 2014 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 imp
 import os.path
 import sys
 
@@ skipping 213 matching lines @@
     """nonempty_parameter_list : nonempty_parameter_list COMMA parameter"""
     p[0] = p[1]
     p[0].Append(p[3])
 
   def p_parameter(self, p):
     """parameter : typename NAME ordinal"""
     p[0] = ast.Parameter(p[2], p[3], p[1],
                          filename=self.filename, lineno=p.lineno(2))
 
   def p_typename(self, p):
-    """typename : basictypename
-                | array
-                | fixed_array
-                | interfacerequest"""
+    """typename : nonnullable_typename QSTN
+                | nonnullable_typename"""
+    if len(p) == 2:
+      p[0] = p[1]
+    else:
+      p[0] = p[1] + "?"
+
+  def p_nonnullable_typename(self, p):
+    """nonnullable_typename : basictypename
+                            | array
+                            | fixed_array
+                            | interfacerequest"""
     p[0] = p[1]
 
   def p_basictypename(self, p):
     """basictypename : identifier
                      | handletype"""
     p[0] = p[1]
 
   def p_handletype(self, p):
     """handletype : HANDLE
                   | HANDLE LANGLE NAME RANGLE"""
@@ skipping 123 matching lines @@
 
 def Parse(source, filename):
   lexer = Lexer(filename)
   parser = Parser(lexer, source, filename)
 
   lex.lex(object=lexer)
   yacc.yacc(module=parser, debug=0, write_tables=0)
 
   tree = yacc.parse(source)
   return tree