Ensure overflow isn't selected when bar is collapsed

After the bubble bar collapsing animation completes, and reordering
is finished, if the bubble overflow is selected, update the selected
bubble to be the first bubble. This ensures that the overflow
is not selected the next time the bubble bar is expanded.

This is done through a callback from the BubbleBarView to the
BubbleBarController with the key of the first bubble. Ideally the view
would just notify that the selected bubble needs to be updated, but
the controller doesn't hold ordering info.

Fixes: 289280431
Test: manual
       - Add 2 bubbles to the bubble bar
       - Expand the bubble bar. The first bubble A should be selected
       - Select the second bubble B
       - Select the overflow
       - Tap on the overflow again to collapse the bubble bar
       - Tap on the bubble bar to expand it
       - Observe that bubble B is first and selected
Change-Id: I0f9c2d628cfaf3a80da55ff634284687425e949a