Revert of remove unused SkAvoidXfermode

samplecode/SampleAll.cpp

Index: samplecode/SampleAll.cpp
diff --git a/samplecode/SampleAll.cpp b/samplecode/SampleAll.cpp
index 16c79c9dbfe3bb2b5e7f53cf3aa6b402cf5f6f6f..537659e0e612d3b6b69893bcbeb74b3d62340f9c 100644
--- a/samplecode/SampleAll.cpp
+++ b/samplecode/SampleAll.cpp
@@ -11,6 +11,7 @@
 #include "SkView.h"
 #include "Sk1DPathEffect.h"
 #include "Sk2DPathEffect.h"
+#include "SkAvoidXfermode.h"
 #include "SkBlurMaskFilter.h"
 #include "SkColorFilter.h"
 #include "SkColorPriv.h"
@@ -572,6 +573,18 @@
         }
 
         canvas->restore();
+
+        if (1) {
+            SkAutoTUnref<SkAvoidXfermode> mode(SkAvoidXfermode::Create(SK_ColorWHITE, 0xFF,
+                                   SkAvoidXfermode::kTargetColor_Mode));
+            SkPaint paint;
+            x += SkIntToScalar(20);
+            SkRect  r = { x, 0, x + SkIntToScalar(360), SkIntToScalar(700) };
+            paint.setXfermode(mode);
+            paint.setColor(SK_ColorGREEN);
+            paint.setAntiAlias(true);
+            canvas->drawOval(r, paint);
+        }
     }
 
 private: