Fix issue with side pages being visible momentarily when swiping up

- Apply the initial scale to overview while it is in the backround app
  state to ensure the side pages are positioned accordingly.  Since this
  affects the computation of the target rects for the overview
  animation, also ensure that we calculate those with the final target
  overview scale applied.

Bug: 117439562
Change-Id: I5e00cf1683e31b22cf937b966d52f8cbe745aaba