Add option to specify number of jobs in sharding supervisor.

tools/sharding_supervisor/sharding_supervisor.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.
 
 """Defer to run_test_cases.py."""
 
 import os
 import optparse
 import sys
@@ skipping 19 matching lines @@
       # run_test_cases so automatic flaky test workaround is still used.
       run_test_cases_extra_args.append('-j1')
       rest.append(arg)
     elif 'browser_tests' in arg:
       # Test cases in this executable fire up *a lot* of child processes,
       # causing huge memory bottleneck. So use less than N-cpus jobs.
       run_test_cases_extra_args.append('--use-less-jobs')
       rest.append(arg)
     else:
       rest.append(arg)
+
+  # Use --jobs arg if exist.
+  for arg in args:
+    if arg.startswith('--jobs='):
+      run_test_cases_extra_args.append(arg)
+      break
+
   return run_test_cases_extra_args, rest
 
 
 def main():
   parser = optparse.OptionParser()
 
   group = optparse.OptionGroup(
       parser, 'Compability flag with the old sharding_supervisor')
   group.add_option(
       '--no-color', action='store_true', help='Ignored')
@@ skipping 24 matching lines @@
 
   run_test_cases_extra_args, rest = pop_known_arguments(args)
 
   import run_test_cases  # pylint: disable=F0401
 
   return run_test_cases.main(cmd + run_test_cases_extra_args + ['--'] + rest)
 
 
 if __name__ == '__main__':
   sys.exit(main())