Remove some old support for PNaCl Scons browser tests.

ppapi/native_client/tools/browser_tester/browser_tester.py

 #!/usr/bin/python
 # Copyright (c) 2012 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.
 
 import glob
 import optparse
 import os.path
 import socket
 import sys
@@ skipping 38 matching lines @@
                     'server to be made visible under the root.')
   parser.add_option('--test_arg', dest='test_args', action='append',
                     type='string', nargs=2, default=[],
                     metavar='KEY VALUE',
                     help='Parameterize the test with a key/value pair.')
   parser.add_option('--redirect_url', dest='map_redirects', action='append',
                     type='string', nargs=2, default=[],
                     metavar='DEST SRC',
                     help='Add a redirect to the HTTP server, '
                     'requests for SRC will result in a redirect (302) to DEST.')
-  parser.add_option('--prefer_portable_in_manifest',
-                    dest='prefer_portable_in_manifest',
-                    action='store_true', default=False,
-                    help='Use portable programs in manifest if available.')
   parser.add_option('-f', '--file', dest='files', action='append',
                     type='string', default=[],
                     metavar='FILENAME',
                     help='Add a file to serve from the HTTP server, to be '
                     'made visible in the root directory.  '
                     '"--file path/to/foo.html" is equivalent to '
                     '"--map_file foo.html path/to/foo.html"')
   parser.add_option('--mime_type', dest='mime_types', action='append',
                     type='string', nargs=2, default=[], metavar='DEST SRC',
                     help='Map file extension SRC to MIME type DEST when '
@@ skipping 291 matching lines @@
   # Validate the URL
   url = options.url
   if url is None:
     parser.error('Must specify a URL')
 
   return Run(url, options)
 
 
 if __name__ == '__main__':
   sys.exit(RunFromCommandLine())