Addition of the entry points for EXT_texture_border_clamp extension. Bug: angleproject:3586 Change-Id: I366c2748213d7fdde815543129320278937000e0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2830146 Commit-Queue: Mohan Maiya <m.maiya@samsung.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
