Add vector GrSLTypes for shorts

Bug: skia:
Change-Id: Icb9eb1fcb0f879cd0bfdd27d06459843361c9947
Reviewed-on: https://skia-review.googlesource.com/62943
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
4 files changed