Changeset [1c81e0eee05dbe7a2080e6f3318db2445acd4904] by Ross Boucher

Closes #429. Doesn't necessarily address the root cause however.

The problem stems from a bug in Safari which is allowing callbacks
to interrupt running code (which should be impossible in JavaScript).
The change essentially makes it so that in the case where this happens,
which is rare, we'll end up accidentally creating an extra iframe.
This isn't ideal, but it also isn't harmful, versus the current
situation where code will simply break.
http://github.com/280north/cappuccino/commit/1c81e0eee05dbe7a2080e6...