[inspector] added headless bot to CQ for inspector CLs

Inspector may change protocol and it can end up with broken headless
bot.

R=dgozman@chromium.org

Bug: none
Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ia813ecebcd509d66ac2291d2836f556e8fb3a096
Reviewed-on: https://chromium-review.googlesource.com/1081338Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53463}

src/inspector/PRESUBMIT.py

@@ -61,6 +61,7 @@ def PostUploadHook(cl, change, output_api):
   return output_api.EnsureCQIncludeTrybotsAreAdded(
     cl,
     [
-      'master.tryserver.blink:linux_trusty_blink_rel'
+      'master.tryserver.blink:linux_trusty_blink_rel',
+      'luci.chromium.try:linux_chromium_headless_rel',
     ],
     'Automatically added layout test trybots to run tests on CQ.')