Thanks for catching this.

I've got several tests for this for out-of-process iframes such as:

https://cs.chromium.org/chromium/src/content/test/data/accessibility/html/iframe-coordinates-cross-process.html

Most of the needed test infrastructure is all in content/ - is there
any way we could test this from content/ or would we need to be in
chrome/?

Also, does this bug depend on whether or not we're in the new OOPIF-based webview vs the old browser-plugin-based, or not?

I'm assuming this bug happens on other platforms too? Easiest to test is with VoiceOver on Mac.

This bug happens both with --disable-features=GuestViewCrossProcessFrames and --enable-features=GuestViewCrossProcessFrames (BrowserPlugin vs oopif webviews).

I will test on a Mac shortly.

I wasn't able to repro with voiceover on Mac. Without cross process frames, the frames rendered correctly.

With cross process frames (oopif webview), i was not able to move focus to the <webview> due to  issue 685739 . I will test again once the fix is rolled into canary.

FWIW, we're seeing a similar issue on the Chrome OS OOBE screen, I'm looking into that now. Not sure if it's related.

I think this is the same root cause at 658947. Feel free to undupe if this doesn't end up getting fixed.