implemented mustImplementGSInvocationsWithLoop workaround in sksl

Third time's the charm

This reverts commit 84cda40bd7e98f4e19574c6e946395e244901408.

Bug: skia:
Change-Id: I2c0f4425122a94beb7b4053ee6e891faa8a5f290
Reviewed-on: https://skia-review.googlesource.com/20441
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
8 files changed