IDL parser: clean up cached lexer table updating code

Source/bindings/scripts/blink_idl_lexer.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 51 matching lines @@
 third_party = os.path.join(module_path, os.pardir, os.pardir, os.pardir, os.pardir)
 # Insert at front to override system libraries, and after path[0] == script dir
 sys.path.insert(1, third_party)
 from ply import lex
 
 # Base lexer is in Chromium src/tools/idl_parser
 tools_dir = os.path.join(third_party, os.pardir, 'tools')
 sys.path.append(tools_dir)
 from idl_parser.idl_lexer import IDLLexer
 
+LEXTAB = 'lextab'
 REMOVE_TOKENS = ['COMMENT']
 
 
 class BlinkIDLLexer(IDLLexer):
     # ignore comments
     def t_COMMENT(self, t):
         r'(/\*(.|\n)*?\*/)|(//.*(\n[ \t]*//.*)*)'
         self.AddLines(t.value.count('\n'))
 
     # Analogs to _AddToken/_AddTokens in base lexer
@@ skipping 11 matching lines @@
         if debug:
             # Turn off optimization and caching to help debugging
             optimize = False
             outputdir = None
         if outputdir:
             # Need outputdir in path because lex imports the cached lex table
             # as a Python module
             sys.path.append(outputdir)
 
             if rewrite_tables:
-                tablefile = os.path.join(outputdir, 'lextab.py')
-
-                def unlink(filename):
+                tablefile_root = os.path.join(outputdir, LEXTAB)
+                # Also remove the .pyc/.pyo files, or they'll be used even if
+                # the .py file doesn't exist.
+                for ext in ('.py', '.pyc', '.pyo'):
                     try:
-                        os.unlink(filename)
+                        os.unlink(tablefile_root + ext)
                     except OSError:
                         pass
 
-                unlink(tablefile)
-                # Also remove the .pyc/.pyo files, or they'll be used even if
-                # the .py file doesn't exist.
-                unlink(tablefile + 'c')
-                unlink(tablefile + 'o')
-
         IDLLexer.__init__(self)
         # Overrides to parent class
         self._RemoveTokens(REMOVE_TOKENS)
         # Optimized mode substantially decreases startup time (by disabling
         # error checking), and also allows use of Python's optimized mode.
         # See: Optimized Mode
         # http://www.dabeaz.com/ply/ply.html#ply_nn15
         self._lexobj = lex.lex(object=self,
                                debug=debug,
                                optimize=optimize,
-                               lextab='lextab',
+                               lextab=LEXTAB,
                                outputdir=outputdir)
 
 
 ################################################################################
 
 def main(argv):
     # If file itself executed, build and cache lex table
     try:
         outputdir = argv[1]
     except IndexError as err:
         print 'Usage: %s OUTPUT_DIR' % argv[0]
         return 1
     # Important: rewrite_tables=True causes the cache file to be deleted if it
     # exists, thus making sure that PLY doesn't load it instead of regenerating
     # the parse table.
     lexer = BlinkIDLLexer(outputdir=outputdir, rewrite_tables=True)
 
 
 if __name__ == '__main__':
     sys.exit(main(sys.argv))