* Hide toolbar when selection is out of view

* properly dispose of toolbar visibility listener

* Add test

* rename toolbarvisibility

* Make visibility for toolbar nullable

* Properly dispose of toolbar visibility listener

* Merge visibility methods into one

* properly dispose of start selection view listener

* Add some docs

* remove unnecessary null check

* more docs

* Update dispose order
Co-authored-by: Renzo Olivares <roliv@google.com>