Don't use divider visibility as indicator for split visibility

* Previously we were using when the divider is visible or not
to notify split visibility listener.
* Now we re-purpose existing setSplitsVisible() method and pass
that value along

Test: Manual, logging
Fixes: 409657406
Flag: EXEMPT bugfix
Change-Id: I1740ddb1ae42d283f546f06a5b3795c034472475