remote_try: Add buildbucket to cbuildbot tryjobs

Added support for sending remote tryjobs configs to buildbucket.

BUG=chromium:498456
TEST=added unit tests. Tested pushing a buildbucket job to test server.

Change-Id: I4ddd03f4a849557a8ad2beee97b508f2e726c00a
Reviewed-on: https://chromium-review.googlesource.com/305261
Commit-Ready: Paul Hobbs <phobbs@google.com>
Tested-by: Paul Hobbs <phobbs@google.com>
Reviewed-by: Paul Hobbs <phobbs@google.com>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index c1c2dab..baf0387 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -461,6 +461,10 @@
       parser,
       'Remote Trybot Options (--remote)')
 
+  group.add_option('--use-buildbucket', default=False, action='store_true',
+                   help=('Use buildbucket instead of git to request'
+                         'the tryjob(s).'))
+
   group.add_remote_option('--hwtest', dest='hwtest', action='store_true',
                           default=False,
                           help='Run the HWTest stage (tests on real hardware)')
@@ -1112,6 +1116,7 @@
       _ConfirmRemoteBuildbotRun()
 
     print('Submitting tryjob...')
+    _SetupConnections(options, build_config)
     tryjob = remote_try.RemoteTryJob(options, args, patch_pool.local_patches)
     tryjob.Submit(testjob=options.test_tryjob, dryrun=False)
     print('Tryjob submitted!')