Fix navigation bar icon invisible with dimming window

Make sure all windows with its frame overlapping with navigation bar can
declare light navigation bar color no matter if it's dimming or not.

Fix: 205308712
Test: atest DisplayPolicyTests
Test: verified dimming window with its frame overlapping with navigation
      bar can declare light navigation bar color.
Change-Id: I6269547f0dfcd54568fd4f07b2642258f93a2822