Add comments to blend coefficient table to help readability

Change-Id: I2ea97fa2fed83fde49155189cd31fee877cd4a69
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307698
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
1 file changed