Investigate whether we can unprefix our current implementation of the specced Fullscreen API, or if we need to do additional work to bring the implementation in line with the spec before unprefixing.
https://github.com/w3c/web-platform-tests/pull/4332
<rdar://problem/37617390>
<rdar://problem/37687680>
*** Bug 242930 has been marked as a duplicate of this bug. ***
Rather than unprefixing our existing implementation (which does not comply with the standard), we will track this work as the new implementation effort in Bug 229333. *** This bug has been marked as a duplicate of bug 229333 ***