Add point spans, but fall back for all cases.

tests/SkLinearBitmapPipelineTest.cpp

Index: tests/SkLinearBitmapPipelineTest.cpp
diff --git a/tests/SkLinearBitmapPipelineTest.cpp b/tests/SkLinearBitmapPipelineTest.cpp
index 8a6ed087c336bd62e284820de37c9ada28039ade..9d12f1b465a83d81acc3260110ca3d60752986fb 100644
--- a/tests/SkLinearBitmapPipelineTest.cpp
+++ b/tests/SkLinearBitmapPipelineTest.cpp
@@ -13,7 +13,7 @@
 struct SinkBilerpProcessor final : public PointProcessorInterface {
     void pointListFew(int n, Sk4fArg xs, Sk4fArg ys) override { fXs = xs; fYs = ys; }
     void pointList4(Sk4fArg Xs, Sk4fArg Ys) override { fXs = Xs; fYs = Ys; }
-
+    void pointSpan(SkPoint start, SkScalar length, int count) override { }
     Sk4f fXs;
     Sk4f fYs;
 };