[DO NOT MERGE] Fix some visual jumps when swiping home

All caused by running the transform progress from 0 to 1 instead of
starting at whatever the progress was before ending the gesture, e.g.:
- When swiping to home without animating into an icon, the corner radius
  was set back to the window corner radius.
- Before this change, the clip didn't update throughout the animation,
  making the window slightly bigger than the floating icon view; after
  this change, the clip jumped to show the insets again before clipping
  back down during the home animation.

Partial backport of ag/Ie48f4b665a5bf3cbef76bdf7f043febe99fb84a0

Bug: 150680980
Change-Id: Ida65097f0ef7d2e11d48b84ecdd353ef89078015