Revert of Remove unused (by clients) SkUnitMapper (https://codereview.chromium.org/283273002/) (https://codereview.chromium.org/288343009/)

Reason for revert:
required blink change failed to land

Original issue's description:
> Remove unused (by clients) SkUnitMapper (https://codereview.chromium.org/283273002/)
>
> This reverts commit dd50c83b5b34dab3a077741861b50ed1f2bc6b8f.
>
> BUG=skia:
>
> Committed: http://code.google.com/p/skia/source/detail?r=14830

R=scroggo@google.com, reed@google.com
TBR=reed@google.com, scroggo@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/296823008

git-svn-id: http://skia.googlecode.com/svn/trunk@14838 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/experimental/SkiaExamples/HelloSkiaExample.cpp b/experimental/SkiaExamples/HelloSkiaExample.cpp
index 6fd2624..0b6c790 100644
--- a/experimental/SkiaExamples/HelloSkiaExample.cpp
+++ b/experimental/SkiaExamples/HelloSkiaExample.cpp
@@ -13,6 +13,7 @@
 #include "SkDraw.h"
 #include "SkGradientShader.h"
 #include "SkGraphics.h"
+#include "SkUnitMappers.h"
 
 class HelloSkia : public SkExample {
 public:
@@ -49,9 +50,12 @@
             };
             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);