Resync web-platform-tests/html/semantics/the-iframe-element from upstream a520598adb3957def27f1b63c6bff62e891ccbda.
Created attachment 409827 [details] Patch
Created attachment 409828 [details] Patch
Created attachment 409838 [details] Patch
Created attachment 409845 [details] Patch
Created attachment 409852 [details] Patch
Committed r267692: <https://trac.webkit.org/changeset/267692> All reviewed patches have been landed. Closing bug and clearing flags on attachment 409852 [details].
<rdar://problem/69681299>