Re-land sksl fragment processor support

This reverts commit ed50200682e0de72c3abecaa4d5324ebcd1ed9f9.

Bug: skia:
Change-Id: I9caa7454b391450620d6989dc472abb3cf7a2cab
Reviewed-on: https://skia-review.googlesource.com/20965
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
55 files changed