Revert "Show the modal overlay as soon as openWindow is called"

Because it's triggering a weird bug in Firefox where
characters are typed into one element and key events
are sent to another element. I have no idea why,
but reverting this fixes it for now.

This reverts commit ca6a16f613e186bec05a481e36dff5eb9f70e0e8.

Bug: 73625
Change-Id: I12dbd5919799ed2bf48b321b396d559a78fb7686
Merge "Revert "Show the modal overlay as soon as openWindow is called""