Scale down expanded view while it is being dragged

Apply a scale to the expanded view while it is dragged.
Pivot the scale from the handle view which is at the top center.

Bug: 283991264
Test: drag expanded view and release it, observe position and scale is
  restored
Test: drag expanded view into dismiss target, observe it is scaled and
  positioned into the center of dismiss target
Test: drag expanded view and release it, collapse the expanded view,
  observe that the collapse animation works as expected
Change-Id: Icd0cdf9f88119e2cbc59d9354a7b8dcd3e2245d5