switch maskfilters to sk_sp

src/c/sk_paint.cpp

Index: src/c/sk_paint.cpp
diff --git a/src/c/sk_paint.cpp b/src/c/sk_paint.cpp
index b48e28fb6dcbddae6eb5f09b7db41aa94ec3d54d..f82cd815c1eadccb65edf099bcd09db5857d9b3c 100644
--- a/src/c/sk_paint.cpp
+++ b/src/c/sk_paint.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include "SkMaskFilter.h"
 #include "SkPaint.h"
 #include "SkShader.h"
 
@@ -68,7 +69,7 @@ void sk_paint_set_shader(sk_paint_t* cpaint, sk_shader_t* cshader) {
 }
 
 void sk_paint_set_maskfilter(sk_paint_t* cpaint, sk_maskfilter_t* cfilter) {
-    AsPaint(cpaint)->setMaskFilter(AsMaskFilter(cfilter));
+    AsPaint(cpaint)->setMaskFilter(sk_ref_sp(AsMaskFilter(cfilter)));
 }
 
 bool sk_paint_is_stroke(const sk_paint_t* cpaint) {