Aligning behavior of LinearLayout divider APIs

Consistency for:
* Early return on calling setter with the current state
* Calling setWillNotDraw when divider is configured with drawable
and visible
* Calling requestLayout to trigger a relayout pass

Also fix a bug that wouldn't show end divider when all non-GONE
children have 0 width/height.

Bug: 28398719
Bug: 28404367
Change-Id: I16796c74a52ac4c3041390c75add2ec3c33bea8b
1 file changed