Task#setTaskDescriptionFromActivityAboveRoot: skip NoDisplay activities.

Given that task description contains elements such as background color,
using activities set to NoDisplay theme (which the color is inherited
from) results in a quick black flash if going to a different activity -
which most trampoline activities do. Skip grabbing task description from
these activities.

Bug: 403497710
Test: Manual - opening activities with NoDisplay theme no longer
flickers a black bar.
Flag: EXEMPT bugfix

Change-Id: I2155fedad98d5e51ae8e7b049487ba92c0dba47a