How should focus and key events work for out-of-process tabs?

This is a restatement of a comment in bug 570620.  In that bug, we now 
have patches to eliminate platform widgets from content processes.

Removing platform widgets from content processes takes us to something 
of a crossroads wrt fennec 2.0a1.  Fennec *renders* just fine without 
platform widgets, but focus and key events are totally broken.  Oleg 
Romashin and I also have code to draw layers in <browser remote=true> 
that are published by widgetless content processes (keys and focus 
similarly borked for <browser remote>).

We definitely want to move away from having platform widgets in content 
processes.  However, I know neither how key events and focus work 
currently, nor how we want them to work for widgetless content 
processes.  If we can make them work without too much effort, I think we 
should take the de-widgetification patches for fennec 2.0a1.  We'll save 
needless rendering to a widget we just draw a canvas over, and work on 
cross-process layers for <browser remote> can continue on m-c without 
disturbing fennec 2.0a1.

Thoughts from those in the know?

Cheers,
Chris