Use sk_sp text blob APIs

gm/textblobmixedsizes.cpp

Index: gm/textblobmixedsizes.cpp
diff --git a/gm/textblobmixedsizes.cpp b/gm/textblobmixedsizes.cpp
index 6ce0eafe629d44f26758954314303fdfc075c5ca..8c51cae45e0221a8b90a704c69bdd50834dc7022 100644
--- a/gm/textblobmixedsizes.cpp
+++ b/gm/textblobmixedsizes.cpp
@@ -80,7 +80,7 @@ protected:
         sk_tool_utils::add_to_text_blob(&builder, text, paint, 0, yOffset);
 
         // build
-        fBlob.reset(builder.build());
+        fBlob = builder.make();
     }
 
     SkString onShortName() override {
@@ -177,7 +177,7 @@ protected:
     }
 
 private:
-    SkAutoTUnref<const SkTextBlob> fBlob;
+    sk_sp<SkTextBlob> fBlob;
 
     static constexpr int kWidth = 2100;
     static constexpr int kHeight = 1900;