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/samplecode/SampleSlides.cpp b/samplecode/SampleSlides.cpp
index b4ebb3c..4748a76 100644
--- a/samplecode/SampleSlides.cpp
+++ b/samplecode/SampleSlides.cpp
@@ -462,8 +462,8 @@
 
 static void r0(SkLayerRasterizer::Builder* rastBuilder, SkPaint& p)
 {
-    p.setMaskFilter(SkBlurMaskFilter::Create(kNormal_SkBlurStyle,
-                                             SkBlurMask::ConvertRadiusToSigma(SkIntToScalar(3))))->unref();
+    p.setMaskFilter(SkBlurMaskFilter::Make(kNormal_SkBlurStyle,
+                                           SkBlurMask::ConvertRadiusToSigma(3)));
     rastBuilder->addLayer(p, SkIntToScalar(3), SkIntToScalar(3));
 
     p.setMaskFilter(nullptr);