Use more robust color transform

Previous code depended on P3 and sRGB being defined with
the same white-point. New code uses a more robust mechanism
that doesn't have that requirement.
Test: run app that uses wide-color, check that nav and status
      haven't changed color
Bug: 29940137

Change-Id: I8cd4c918567f126b17ebfb51e37fc52515d08308