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/bigblurs.cpp b/gm/bigblurs.cpp
index d68b2ca..5c09ab9 100644
--- a/gm/bigblurs.cpp
+++ b/gm/bigblurs.cpp
@@ -70,8 +70,7 @@
 
         for (int i = 0; i < 2; ++i) {
             for (int j = 0; j <= kLastEnum_SkBlurStyle; ++j) {
-                SkMaskFilter* mf = SkBlurMaskFilter::Create((SkBlurStyle)j, kSigma);
-                blurPaint.setMaskFilter(mf)->unref();
+                blurPaint.setMaskFilter(SkBlurMaskFilter::Make((SkBlurStyle)j, kSigma));
 
                 for (int k = 0; k < (int)SK_ARRAY_COUNT(origins); ++k) {
                     canvas->save();