Move validation from Intermediate::addUnaryMath to ParseContext Intermediate should only have logic for creating node objects, validation of parameter types belongs in ParseContext. BUG=angleproject:952 TEST=angle_unittests, WebGL conformance tests Change-Id: Ie90697641fabb2a837ccc4571a93616d63ea64e6 Reviewed-on: https://chromium-review.googlesource.com/262414 Tested-by: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Nicolas Capens <capn@chromium.org>