Followup 571d6cac: when the selection changes, undo highlights

Ignoring all bounced change events led to the logic for unhighlighting
the previously selected FocusableNode being skipped. This caused a bug
where if you clicked a FocusableNode, it would stay highlighted even
if you then selected some text, until you highlighted another node
(which would then be highlighted forever, etc.)

Change-Id: Ia8d74ef85eaa47326d49ef6c0f395b44b90da4dc