STR: * Open browser and load a website * Press Home * Open third-party app and load a custom tab Expected: Only custom tab UI should be visible Actual: Browser toolbar is visible (in web content?) while website is loading Device: Google Pixel XL (Android 7.1.2)

A similar bug was fixed in bug 1358805.

Does this happen every time for you? I tried to reproduce with out success in Nightly. I saw other issues such as trying to open the custom tab in Firefox just kicking me back to the custom tab the first time but could never get the static toolbar snapshot to show up.

It doesn't happen every time - but often enough to be noticeable and confusing while normal usage. Note that this only happens while the website is loading and doesn't paint anything yet (I guess). I assume it is more likely if the page is loading slowly. I thought it's more likely to happen while the page in Fennec is loading too - but this doesn't seem to be the case after some more testing.

I'd like to wait until the geckoview version has landed. I'm hoping this will fix the issue since the custom tabs should get their own toolbar animator which will be in a known state instead of inheriting Fennec's.

I haven't seen this at all since we're using GeckoView.