This helps with debugging precision propagation issues.

BUG=angle:787

Change-Id: Ia969481c8d933455cdafef4ae25c6ab3946bc1c2
Reviewed-on: https://chromium-review.googlesource.com/224281Reviewed-by: Nicolas Capens <capn@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Shannon Woods <shannonwoods@chromium.org>