On IE6 or IE8 we can't abuse an IFrame quite the same way as we
do on Mozilla, WebKit and Opera. IE requires us to initialize the
iframe by running a script that exports the iframe window back to
the parent before we can use its eval method.
Change-Id: Ia5e01a611ed9685a5fc5341a3f8a2446f7dcb9f4
Signed-off-by: Shawn O. Pearce <sop@google.com>