Add script for triggering Buildbucket builds

BUG=493885
TESTED=See https://paste.googleplex.com/5622248052359168

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=295569

R=nodir@chromium.org

Review URL: https://codereview.chromium.org/1164363003.

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@295570 0039d316-1c4b-4281-b951-d872f2087c98

buildbucket.py

@@ -43,6 +43,7 @@ def main(argv):
   subparsers = parser.add_subparsers(dest='command')
   put_parser = subparsers.add_parser('put')
   put_parser.add_argument(
+    '-b',
     '--bucket',
     help=(
       'The bucket to schedule the build on. Typically the master name, e.g.'