use Make instead of Create to return a shared shader

samplecode/SampleColorFilter.cpp

Index: samplecode/SampleColorFilter.cpp
diff --git a/samplecode/SampleColorFilter.cpp b/samplecode/SampleColorFilter.cpp
index af1cd935a2d6811719de08074291a2f2882e9182..4ee8949410e58f72b3b41ee3b962081774eca6f0 100644
--- a/samplecode/SampleColorFilter.cpp
+++ b/samplecode/SampleColorFilter.cpp
@@ -111,7 +111,7 @@ static SkBitmap createBitmap(int n) {
 
 class ColorFilterView : public SampleView {
     SkBitmap fBitmap;
-    SkShader* fShader;
+    sk_sp<SkShader> fShader;
     enum {
         N = 64
     };
@@ -126,10 +126,6 @@ public:
         }
     }
 
-    virtual ~ColorFilterView() {
-        fShader->unref();
-    }
-
 protected:
     // overrides from SkEventSink
     virtual bool onQuery(SkEvent* evt) {