Spec out the PLS client API Drafts the additions to the OpenGL ES 3.0 spec for pixel local storage. Bug: angleproject:7279 Change-Id: Ibc0d227142ac51f5d3820f27c9114779d846ffc2 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3824171 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>