switched gl_Position and gl_PointSize to sk_*

Bug: skia:
Change-Id: Ie7508991aa975c1400bac23ae49d81041a313968
Reviewed-on: https://skia-review.googlesource.com/51320
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
17 files changed