[strace] Add support for interrupted calls and proper chdir handling.

tools/isolate/isolate_test.py

 #!/usr/bin/env 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 hashlib
 import json
 import logging
 import os
 import re
@@ skipping 37 matching lines @@
     if not read_only:
       min_mode |= 0200
     def mode(filename):
       return (min_mode | 0111) if filename.endswith('.py') else min_mode
     expected = {
       u'command':
         [unicode(sys.executable)] +
           [unicode(x) for x in args],
       u'files': dict((unicode(f), {u'mode': mode(f)}) for f in files),
       u'relative_cwd': u'.',
+      u'read_only': False,
     }
     if with_hash:
       for filename in expected[u'files']:
         # Calculate our hash.
         h = hashlib.sha1()
         h.update(open(os.path.join(ROOT_DIR, filename), 'rb').read())
         expected[u'files'][filename][u'sha-1'] = h.hexdigest()
 
     actual = json.load(open(self.result, 'rb'))
     self.assertEquals(expected, actual)
@@ skipping 185 matching lines @@
   if sys.argv[1] == '--ok':
     return 0
   if sys.argv[1] == '--fail':
     return 1
 
   unittest.main()
 
 
 if __name__ == '__main__':
   sys.exit(main())