Use logdog butler subcommand to run tests.

tools/mb/mb.py

Index: tools/mb/mb.py
diff --git a/tools/mb/mb.py b/tools/mb/mb.py
index edbb434d27bfb36a9f3f4d1e8c0ab59231e909a3..007194be0a9ef6316ee804b2578628f13a1a4493 100755
--- a/tools/mb/mb.py
+++ b/tools/mb/mb.py
@@ -1086,23 +1086,9 @@ class MetaBuildWrapper(object):
                                 output_path=None)
 
     if android and test_type != "script":
-      logdog_command = [
-          '--logdog-bin-cmd', './../../bin/logdog_butler',
-          '--project', 'chromium',
-          '--service-account-json',
-          '/creds/service_accounts/service-account-luci-logdog-publisher.json',
-          '--prefix', 'android/swarming/logcats/${SWARMING_TASK_ID}',
-          '--source', '${ISOLATED_OUTDIR}/logcats',
-          '--name', 'unified_logcats',
-      ]
-      test_cmdline = [
-          self.PathJoin('bin', 'run_%s' % target),
-          '--logcat-output-file', '${ISOLATED_OUTDIR}/logcats',
-          '--target-devices-file', '${SWARMING_BOT_FILE}',
-          '-v'
-      ]
-      cmdline = (['./../../build/android/test_wrapper/logdog_wrapper.py']
-                 + logdog_command + test_cmdline)
+      cmdline = [

[jbudorick, 2017/02/27 22:49:15]

I do think mb.py should at least know about <output dir>/bin/run_<target>

[BigBossZhiling, 2017/02/28 07:29:53]

Done.

+          '../../build/android/test_wrapper/logdog_wrapper.py',
+          '--target', target]
     elif use_xvfb and test_type == 'windowed_test_launcher':
       extra_files = [
           '../../testing/test_env.py',