Make PiP reentry state to use scale instead of size

Beforehand the state was using fixed size, which could be below minimum
size for a given screen size, e.g. after you fold/unfold the device.

This change makes it so that the bounds scale is used instead of size,
which makes the PiP size always align with PiP Size Spec after reentry.

Bug: 316249837
Test: before http://recall/-/ekEuGtt9d9HWqkUtAzpHx8/fiQwpwJW7bnFUeuop8olCB
Test: after http://recall/-/ekEuGtt9d9HWqkUtAzpHx8/gVg5R7FmwHU5xrxplIHsGH
Flag: none

Change-Id: I9962a40ccf5e96ab544f580740f5d2870ea8121d