Revert of Remove unused (by clients) SkUnitMapper (https://codereview.chromium.org/283273002/)

samplecode/SampleVertices.cpp

Index: samplecode/SampleVertices.cpp
diff --git a/samplecode/SampleVertices.cpp b/samplecode/SampleVertices.cpp
index 1e568f55689b96bf6a37d22b5d01c373919fbab0..4c3a17eb004bc394cbac09b961b01b492f2bd856 100644
--- a/samplecode/SampleVertices.cpp
+++ b/samplecode/SampleVertices.cpp
@@ -47,7 +47,7 @@
                       { SkIntToScalar(size.fX), SkIntToScalar(size.fY) } };
     SkColor colors[] = { SK_ColorRED, SK_ColorGREEN, SK_ColorBLUE, SK_ColorRED };
     return SkGradientShader::CreateLinear(pts, colors, NULL,
-                    SK_ARRAY_COUNT(colors), SkShader::kMirror_TileMode);
+                    SK_ARRAY_COUNT(colors), SkShader::kMirror_TileMode, NULL);
 }
 
 class VerticesView : public SampleView {