GitLab

* Prep for athena on chrome.

Another notable change:
* pass app_id to AppActivity. it's known at creation time.

Note: this depends on https://codereview.chromium.org/505273002/

BUG=397167

Review URL: https://codereview.chromium.org/501093003

Cr-Commit-Position: refs/heads/master@{#292264}