Fix frame switching after frame redirect/creation (follow on)

Continuation of #1177.

@mrmr1993:  I did some tidy up of #1177.  Could you double check, please, and also check the comment (which I will make in a few moments) below?
@mrmr1993:  Is this the right thing to do?

We have no idea if we're focusing the right frame.  And, presumably, a `handleFrameFocused` request will come through to tell us which frame has the focus.  And if we do this, then there's a race condition.