Add --mode=noop so progress can be made while the builders are being reconfigured

tools/isolate/isolate.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.
 
 """Does one of the following depending on the --mode argument:
   check     Verifies all the inputs exist, touches the file specified with
             --result and exits.
   hashtable Puts a manifest file and hard links each of the inputs into the
             output directory.
+  noop      Do nothing, used for transition purposes.
   remap     Stores all the inputs files in a directory without running the
             executable.
   run       Recreates a tree with all the inputs files and run the executable
             in it.
   trace     Runs the executable without remapping it but traces all the files
             it and its child processes access.
 
 See more information at
 http://dev.chromium.org/developers/testing/isolated-testing
 """
@@ skipping 490 matching lines @@
   logging.debug('processed infiles: %s' % infiles)
   return root_dir, infiles, data
 
 
 def main():
   default_variables = [('OS', trace_inputs.get_flavor())]
   if sys.platform in ('win32', 'cygwin'):
     default_variables.append(('EXECUTABLE_SUFFIX', '.exe'))
   else:
     default_variables.append(('EXECUTABLE_SUFFIX', ''))
-  valid_modes = get_valid_modes()
+  valid_modes = get_valid_modes() + ['noop']
   parser = optparse.OptionParser(
       usage='%prog [options] [.isolate file]',
       description=sys.modules[__name__].__doc__)
   parser.format_description = lambda *_: parser.description
   parser.add_option(
       '-v', '--verbose',
       action='count',
       default=int(os.environ.get('ISOLATE_DEBUG', 0)),
       help='Use multiple times')
   parser.add_option(
@@ skipping 24 matching lines @@
   logging.basicConfig(
       level=level,
       format='%(levelname)5s %(module)15s(%(lineno)3d): %(message)s')
 
   if not options.mode:
     parser.error('--mode is required')
   if len(args) != 1:
     logging.debug('%s' % sys.argv)
     parser.error('Use only one argument which should be a .isolate file')
 
+  if options.mode == 'noop':
+    # This undocumented mode is to help transition since some builders do not
+    # have all the test data files checked out. Exit silently.
+    return 0
+
   root_dir, infiles, data = process_options(
       dict(options.variables), options.result, args[0], parser.error)
 
   try:
     resultcode, data = isolate(
         options.outdir,
         options.mode,
         root_dir,
         infiles,
         data)
   except run_test_from_archive.MappingError, e:
     print >> sys.stderr, str(e)
     return 1
   save_results(options.result, data)
   return resultcode
 
 
 if __name__ == '__main__':
   sys.exit(main())