Drop unused support for MSAA sample locations

Bug: skia:
Change-Id: I96f0c25732d79c5881e400b121e81c5696a747a6
Reviewed-on: https://skia-review.googlesource.com/107441
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
20 files changed