Pass the bubble bar screen coordinates to WMShell

This allows WMShell to store the bubble bar coordinates so that it
draw the expanded view above it.

Fixes: 290099589
Test: Manual
       - Add bubbles to the bubble bar
       - Expand the bubble bar
       - Observe that there is enough space between the bar and the
         expanded view
Change-Id: Iff40b2b71369f33f343eb069e119f65723a6984e