Add support for PLS as function arguments Bug: angleproject:7279 Change-Id: I89d5c02148cbdbbd02dc4840ffada2c96c2a849b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3767534 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Chris Dalton <chris@rive.app>