Postponing registering widget listener

For the swipe-to-home gesture, the call will happen
after the animation.

This fixes jank during swiping up from an ap
to home.

Also renaming some methods for clarity.

Bug: 175048504, 173072373
Test: tracing
Change-Id: I070b23edb633d2ac0985d5eb9f75c789f8569772