If an iframe is removed from the DOM after the SafariDriver has focused on it, the driver
will hang.

This is because removing the iframe triggers an unload event, which the extension will
receive and block on.  Since the frame was removed and not just loading a new page,
there will never be a corresponding load event to unblock the extension.

At this point we know two things to be true:
1) This is bad and should be fixed.
2) iframes are evil.