remove shadeSpan4f()

This shouldn't cause any diffs, provided I've implemented the no-stages
shadeSpan() fallback correctly.  (I'm not sure which shaders don't have
stages at this point.)

Bug: skia:8730
Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Change-Id: Ia0d777b526e05b7262ff77daec5ef4d8b0afdb9b
Reviewed-on: https://skia-review.googlesource.com/c/188031
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
5 files changed