Bugzilla

I've repeated the test, this time without interacting with the iframe whatsoever, and did indeed reach a different conclusion. 
Just to make sure we're on the same page, my steps were:

I've repeated the test, this time without interacting with the iframe whatsoever, and did indeed reach a different conclusion. 
Just to make sure we're on the same page, my steps were:
1. Reach the page
2. Click the Full Screen Parent Page button

with these steps I've arrived to this build:
DEBUG : Found commit message:
Bug 1129227 - Part 3: Add test for requesting fullscreen in async callback; r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D47152