Implement trunc, round, roundEven (Emulated roundEven) BUG=angle:934 Change-Id: If33256bf3707f3f0202147276c71f08c65518205 Reviewed-on: https://chromium-review.googlesource.com/254842 Reviewed-by: Olli Etuaho <oetuaho@nvidia.com> Tested-by: Olli Etuaho <oetuaho@nvidia.com>