Implement updated method overriding rules in the vm.

runtime/tools/create_snapshot_bin.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 """Script to create snapshot bin file."""
 
 import getopt
 import optparse
@@ skipping 55 matching lines @@
   if not ProcessOptions(options):
     parser.print_help()
     return 1
 
   # If there are additional arguments, report error and exit.
   if args:
     parser.print_help()
     return 1
 
   # Setup arguments to the snapshot generator binary.
-  script_args = ["--error_on_malformed_type"]
+  script_args = ["--error_on_malformed_type", "--error_on_bad_override"]
 
   # First setup the snapshot output filename.
   script_args.append(''.join([ "--snapshot=", options.output_bin ]))
 
   # Next setup all url mapping options specified.
   for url_arg in options.url_mapping:
     url_mapping_argument = ''.join(["--url_mapping=", url_arg ])
     script_args.append(url_mapping_argument)
 
   # Finally append the script name if one is specified.
   if options.script:
     script_args.append(options.script)
 
   # Construct command line to execute the snapshot generator binary and invoke.
   command = [ options.executable ] + script_args
   try:
     utils.RunCommand(command, outStream=sys.stderr, errStream=sys.stderr,
                      verbose=options.verbose, printErrorInfo=True)
   except Exception as e:
     return -1
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())