Reduce surface size when allocating intercept layer

- Specify the smallest surface size while still declaring a large enough
  touchable region to receive touches for the whole display. We don't
  use w/h of 0,0 or MATCH_PARENT as those technically result in an
  unbounded touch region, but that may be fixed in a future change.

Bug: 433055104
Flag: EXEMPT bugfix
Test: Manual
Change-Id: I4ee7700c4c4cff1fc812ee04aa607299bfac9858