switch maskfilters to sk_sp

gm/textblobmixedsizes.cpp

Index: gm/textblobmixedsizes.cpp
diff --git a/gm/textblobmixedsizes.cpp b/gm/textblobmixedsizes.cpp
index b2697a8cf4aff63db36717329adb7bfc99ad42ab..82a0dbbd2aac392f158c39b6630ad21b5010c6c2 100644
--- a/gm/textblobmixedsizes.cpp
+++ b/gm/textblobmixedsizes.cpp
@@ -135,9 +135,8 @@ protected:
         // setup blur paint
         SkPaint blurPaint(paint);
         blurPaint.setColor(sk_tool_utils::color_to_565(SK_ColorBLACK));
-        SkAutoTUnref<SkMaskFilter> mf(SkBlurMaskFilter::Create(kNormal_SkBlurStyle, kSigma));
-        blurPaint.setMaskFilter(mf);
-
+        blurPaint.setMaskFilter(SkBlurMaskFilter::Make(kNormal_SkBlurStyle, kSigma));
+        
         for (int i = 0; i < 4; i++) {
             canvas->save();
             switch (i % 2) {