Add abs stage to Raster Pipeline.

Change-Id: I2f67c26d79ea730a0ba7df09b1227c3b55261ff0
Bug: skia:13676
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/626238
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
3 files changed