Correct PiP inset adjustment.

We want to calculate the scaling factor we need to have
the content area of the surface (not including insets) to reach
our desired size, otherwise we will seem to scale the insets
up or down over time.

Bug: 28559097
Change-Id: I86dbd5fc902b5d380d33dba626c6694b3c57ff25
1 file changed