Fix crrev and add test coverage for the main function.

scripts/slave/recipe_modules/crrev/resources/crrev_client.py

 #!/usr/bin/python
 # Copyright 2016 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.
 
 """A simple client for the crrev.com API.
 
 API Explorer page: https://goo.gl/5ThLDm
 
 Example usage:
@@ skipping 43 matching lines @@
       if attempt >= attempts:
         raise
       logging.exception('Failed to request from crrev: %s', e)
 
     logging.info('Sleeping %d seconds before retry (%d/%d).',
                  retry_delay_seconds, attempt, attempts)
     time.sleep(retry_delay_seconds)
     retry_delay_seconds *= 2
 
 
-def main():
+def main(args):
   parser = argparse.ArgumentParser()
   parser.add_argument('path', help='Path + query to add onto the base URL.')
   parser.add_argument('--params-file', help='Request parameter JSON file.')
   parser.add_argument('--attempts', default=1, help='Number of times to retry.')
-  args = parser.parse_args()
+  args = parser.parse_args(args)
   params = {}
   if args.params_file:
-    params = json.lad(args.params_file)
-  print json.dumps(crrev_get(args.path, params, args.attempts), indent=2)
+    params = json.load(open(args.params_file))
+  return json.dumps(crrev_get(args.path, params, args.attempts), indent=2)
 
 
 if __name__ == '__main__':
-  main()
+  print main(sys.argv[1:])