Don't draw synchronously in onResume()

this could cause a dead-lock if the applicaltion's draw
implementation blocks until something happenson the main
ui thread.

note: we're still doing this synchronous draw in onWindowResize() because
that's what the previous implementation did. Technically, it has the
same problem.

Bug: 8586305
Change-Id: I782568289cc9419346aeea73775d86faa28b3058