Respect manually set HARDWARE_ACCELERATED flag.

When choosing what window parameters to pass on
to child windows, we need to respect the manually set
FLAG_HARDWARE_ACCELERATED from Window.setFlags() in
addition to the activity manifest value, and the value
from setWindowManager. Given that we pass the value
on to child windows from when setWindowManager is called,
I think it makes sense to pass it when setFlags is
called.

Bug: 27099358
Bug: 23036374
Change-Id: Ie018841aadd270910fe0f8bc5a5ddca3bfbee69b