Add point spans, but fall back for all cases.

tests/SkLinearBitmapPipelineTest.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLinearBitmapPipeline.h"
 #include "SkColor.h"
 #include "SkPM4f.h"
 #include "Test.h"
 
 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;
 };
 
 using Pixel = float[4];
 DEF_TEST(SkBitmapFP, reporter) {
 
     int width = 10;
     int height = 10;
     uint32_t* bitmap = new uint32_t[width * height];
@@ skipping 30 matching lines @@
                pixelBuffer[i][1] * 255.0f,
                pixelBuffer[i][2] * 255.0f,
                pixelBuffer[i][3] * 255.0f);
     }
 #endif
 
     delete [] bitmap;
     delete [] FPbuffer;
 }