https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Android%20%28Nexus4%29 screenshot: https://screenshot.googleplex.com/kTE0KXu7uPS
and 
https://luci-milo.appspot.com/buildbot/chromium.webkit/WebKit%20Android%20%28Nexus4%29/ screenshot: https://screenshot.googleplex.com/ryovED4Pbsz

Show different build information (for the same builder?). +hinoka@ is there some skew expected here? Luci-milo looks like it's at least 6 builds behind buildbot.

That's really weird, i'm not seeing anything obviously wrong with the pubsub pipeline:
https://app.google.stackdriver.com/services/cloud_pubsub/topics/luci-milo/public-buildbot-1106935?project=luci-milo

I'll dig in deeper

There it is

https://pantheon.corp.google.com/logs/viewer?project=luci-milo&minLogLevel=0&expandAll=false&resource=gae_app%2Fmodule_id%2Fpubsub%2Fversion_id%2F1903-ff21376&logName=projects%2Fluci-milo%2Flogs%2Fappengine.googleapis.com%252Frequest_log&filters=text:chromium.webkit&timestamp=2017-08-03T18:57:08.139703000Z

Milo hasn't received a pubsub message from chromium.webkit since 11am.

We can probably alert about this from the GAE side...

not a SoM issue but please assign an appropriate component