Set position during shrink animation.

When performing a drag to desktop, the initial task shrinking animation
sets scale via an animation and position based on input. This resulted
in the task moving away from the pointer if the pointer stopped moving,
as only scale would be updated.

This CL changes the positioning such that scale and position are updated
at the same time while the task is animating, keeping the handle under
the pointer as it is dragged.

Bug: 315520199
Test: Manual, drag with both finger and mouse
Change-Id: I2efdb85dba54b5e8b4536b471c3ff07388f6add8