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

experimental/SkiaExamples/HelloSkiaExample.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  */
 
 #include "SkExample.h"
 
 #include "SkApplication.h"
 #include "SkDraw.h"
 #include "SkGradientShader.h"
 #include "SkGraphics.h"
+#include "SkUnitMappers.h"
 
 class HelloSkia : public SkExample {
 public:
     HelloSkia(SkExampleWindow* window) : SkExample(window) {
         fName = "HelloSkia";
         fBGColor = SK_ColorWHITE;
         fRotationAngle = SkIntToScalar(0);
 
         fWindow->setupBackend(SkExampleWindow::kGPU_DeviceType);
         // Another option is software rendering:
@@ skipping 16 matching lines @@
         canvas->drawRect(rect, paint);
 
         // Set up a linear gradient and draw a circle
         {
             SkPoint linearPoints[] = {
                     {SkIntToScalar(0), SkIntToScalar(0)},
                     {SkIntToScalar(300), SkIntToScalar(300)}
             };
             SkColor linearColors[] = {SK_ColorGREEN, SK_ColorBLACK};
 
+            SkUnitMapper* linearMapper = new SkDiscreteMapper(100);
+            SkAutoUnref lm_deleter(linearMapper);
+
             SkShader* shader = SkGradientShader::CreateLinear(
                     linearPoints, linearColors, NULL, 2,
-                    SkShader::kMirror_TileMode);
+                    SkShader::kMirror_TileMode, linearMapper);
             SkAutoUnref shader_deleter(shader);
 
             paint.setShader(shader);
             paint.setFlags(SkPaint::kAntiAlias_Flag);
 
             canvas->drawCircle(SkIntToScalar(200), SkIntToScalar(200),
                     SkIntToScalar(64), paint);
 
             // Detach shader
             paint.setShader(NULL);
@@ skipping 32 matching lines @@
     SkScalar fRotationAngle;
     SkColor fBGColor;
 };
 
 static SkExample* MyFactory(SkExampleWindow* window) {
     return new HelloSkia(window);
 }
 
 // Register this class as a Skia Example.
 SkExample::Registry registry(MyFactory);