Repro: 
1. Install and build lighthouse from master
2. Use Chromium ToT (or 2 days old canary)
3. lighthouse https://www.example.com
4. Wait for the 4th reload of the page, when you'll see the overlay on top of the page

There is no `debugger;` on the page. It happens on all pages.

Removing debugger.enable doesn't affect it. we still see the overlay.

Attached is the protocol traffic right before the navigation where it shows up.
It looks like it may have to do with earlier methods, however -- i attempted to remove the earlier passes and could no longer repro.

The tab is on about:blank and page.navigate is called. the overlay becomes visible on the first paint of the page after navigation.



 

Deleted: overlay.png 24.2 KB

	overlay.png 24.2 KB View Download

Deleted: Screen Shot 2017-04-27 at 6.45.28 PM.png 350 KB

	Screen Shot 2017-04-27 at 6.45.28 PM.png 350 KB View Download