Fix virtual display nesting

This fixes the cycling rendering loop caused by nesting virtual
displays by preventing them from recomposing if their contents
haven't changed.

(cherry-pick from master I600365c0fd5d3ad93e04295d26cf9de177ffc79b)

Bug: 12101046
Change-Id: I6182993d53537781aedb522f97a50f06eed8b80f
8 files changed