Fix Snackbar not showing after a dismissal

Caused by us only dipatching a layout change callback
if 'changed' == true. That won't always be true though
if the layout's contents have changed.

The functionality is ambigiuous in that we have
never documented it, but it's simple enough to support.

BUG: 27064954
Change-Id: I517ebde0ed89a2bddf04aef15535baf1e70b1aa4
1 file changed