Apps which do not support density cannot be resized

This is to prevent apps which do not support density
(so essentially pre-Doughnut) from being resized and / or
windowed in free form mode.

These apps are rendered into a smaller sized buffer and
then scaled onto the screen. Using freeform window mode with
these apps uncovered many different problems.

Bug: 33843467
Test: Pre-N as well as Pre-Doughnut applications are presented
properly in free form mode. (Pre-Doughnut cannot be windowed /
resized, many M apps can).
Change-Id: I3c0eb3681486dc85ace15955432d79200743bce3