Add vector GrSLTypes for shorts

Bug: skia:
Change-Id: I686950df9f5470b4885823471957c3859cc692ea
Reviewed-on: https://skia-review.googlesource.com/63441
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
4 files changed