Tuning app close, and turn on flag.

- Tracks centery, slowed things down a bit

* We will be replacing StaggeredWorkspaceAnim with
  another animation, but I'm keeping it here in
  case we decide to turn the flag off later on.

Bug: 173107751
Test: manual
Change-Id: I5cd54ec374ad07c4912aff125a905b3b1dc7ebd5