This reverts commit cb09a27cc2.
The class is not very useful as it is now, due to performance issues
(T169027#9342985). The Graph extension is not going to use iframes
(T334940#9537862) and that was the only concrete feature for this, so
making the class usable in practice is unlikely to get prioritized.
No point in leaving the code in its current halfway state.
Bug: T222807
Bug: T169027
Change-Id: Id1b5193975435b58aebc225528e30f04456d0c41
038ec7be40