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

This reverts commit dd50c83b5b34dab3a077741861b50ed1f2bc6b8f.

BUG=skia:
R=scroggo@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/288343009

git-svn-id: http://skia.googlecode.com/svn/trunk@14830 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/samplecode/SampleLayers.cpp b/samplecode/SampleLayers.cpp
index 51f02a1..43f5d42 100644
--- a/samplecode/SampleLayers.cpp
+++ b/samplecode/SampleLayers.cpp
@@ -31,7 +31,7 @@
     SkColor colors[] = { 0, SK_ColorWHITE };
     SkPoint pts[] = { { 0, 0 }, { 0, SK_Scalar1*20 } };
     SkShader* s = SkGradientShader::CreateLinear(pts, colors, NULL, 2, SkShader::kClamp_TileMode,
-                                                 NULL, 0, &localMatrix);
+                                                 0, &localMatrix);
 
     paint->setShader(s)->unref();
     paint->setXfermodeMode(SkXfermode::kDstIn_Mode);