FloatingToolbar: Fix orientation change handling.

Orientation change handling was done using a config change listener
but it is not a sufficient trigger for when the toolbar needs to be
resized. It is called before the layout has changed. A better trigger
for resizing the toolbar will be on layout change. At this time, we
get an accurate measurement of the drawing area.

Bug: 21816857
Change-Id: Ia4d752f12b64b64256c1c41d5ede5d2e29a4f408