Add a test for gl_VertexID BUG=angleproject:1217 BUG=587781 Change-Id: I2fd20c686863c1409228717606977a3c4e1cd7fa Reviewed-on: https://chromium-review.googlesource.com/338180 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Corentin Wallez <cwallez@chromium.org>