Revert "Merge pull request #2819 from bjwbell/iframe-layers"

This reverts commit 0200b61f713f2cdddcbc06ccd4cb5de11332899a, reversing
changes made to ca968219025a46e57b5cd770ae7c8ac5919876b1.
Merge pull request #2880 from zwarich/iframes-revert

Revert "Merge pull request #2819 from bjwbell/iframe-layers"