Don't use glFrontFace

This is an exploratory commit to see if glFrontFace is the cause of
a recent perf regression. Instead we invert gl_FrontFacing in SkSL.

Bug: skia:
Change-Id: Ida6f6435785e814c089ad34ba2f32793c4ac23c4
Reviewed-on: https://skia-review.googlesource.com/144410
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
4 files changed