Modified the way icons merge into the shelf

The icon can now also move into the shelf in an animated
way instead of just moving out of it.

Change-Id: Iba4ebd3cd48b5299b89bd0cb2b05bd318e352173
Fixes: 33463805
Test: add notification observe behavior when scrolling
(cherry picked from commit a1d9790735a183578ad8789234b7defd67ed0866)
3 files changed