Submit tryjobs automatically on upload

R=viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/1128183008
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index bbf3dfc..5846af1 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -1134,3 +1134,8 @@
   ]
 
   return GetDefaultTryConfigs(builders)
+
+def PostUploadHook(cl, change, output_api):
+  import subprocess
+  subprocess.check_call(["git", "cl", "try"])
+  return []