Create Raster Pipeline 'add' ops for ints and floats.

These always operate on data which is adjacent in memory, and write
their output data into the first input.

Change-Id: I39c6f1d838e3f10c886afe34a1f28352da627c3b
Bug: skia:13676
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/610179
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
4 files changed