switch maskfilters to sk_sp

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1852113003

Review URL: https://codereview.chromium.org/1852113003
diff --git a/gm/blurrect.cpp b/gm/blurrect.cpp
index 0fe866f..8aae04a 100644
--- a/gm/blurrect.cpp
+++ b/gm/blurrect.cpp
@@ -83,7 +83,7 @@
 typedef void (*PaintProc)(SkPaint*, SkScalar width);
 
 class BlurRectGM : public skiagm::GM {
-      SkAutoTUnref<SkMaskFilter> fMaskFilters[kLastEnum_SkBlurStyle + 1];
+      sk_sp<SkMaskFilter> fMaskFilters[kLastEnum_SkBlurStyle + 1];
       SkString  fName;
       SkAlpha   fAlpha;
 public:
@@ -95,9 +95,9 @@
 protected:
     void onOnceBeforeDraw() override {
         for (int i = 0; i <= kLastEnum_SkBlurStyle; ++i) {
-            fMaskFilters[i].reset(SkBlurMaskFilter::Create((SkBlurStyle)i,
+            fMaskFilters[i] = SkBlurMaskFilter::Make((SkBlurStyle)i,
                                   SkBlurMask::ConvertRadiusToSigma(SkIntToScalar(STROKE_WIDTH/2)),
-                                  SkBlurMaskFilter::kHighQuality_BlurFlag));
+                                  SkBlurMaskFilter::kHighQuality_BlurFlag);
         }
     }