webrtc is doing this already (go/webrtc-binary-sizes). Attached a screenshot of what it looks like.

* Their plugin is here:
  https://chromium.googlesource.com/infra/gerrit-plugins/binary-size/
* It's a fork of:
  https://chromium.googlesource.com/infra/gerrit-plugins/buildbucket/

We could either create a separate plugin, or modify the webrtc one to support our metric format. The fundamental difference is that android-binary-size builds both before & after patch, whereas webrtc's plugin assumes the bot builds only "after", and fetches the "before" metric from a waterfall bot.
 

Deleted: Screen Shot 2019-01-11 at 1.17.28 PM.png 41.1 KB

	Screen Shot 2019-01-11 at 1.17.28 PM.png 41.1 KB View Download