Use sk_sp text blob APIs

SkTextBlobBuilder::build()      -> make()
SkAutoTUnref<const SkTextBlob>  -> sk_sp<SkTextBlob>
drawTextBlob(const SkTextBlob*) -> drawTextBlob(const sk_sp<SkTextBlob>&)

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2335493005

Review-Url: https://codereview.chromium.org/2335493005
diff --git a/gm/lcdoverlap.cpp b/gm/lcdoverlap.cpp
index de159e1..623d746 100644
--- a/gm/lcdoverlap.cpp
+++ b/gm/lcdoverlap.cpp
@@ -44,7 +44,7 @@
         paint.setSubpixelText(true);
         paint.setLCDRenderText(true);
         sk_tool_utils::add_to_text_blob(&builder, text, paint, 0, 0);
-        fBlob.reset(builder.build());
+        fBlob = builder.make();
     }
 
     SkISize onISize() override { return SkISize::Make(kWidth, kHeight); }
@@ -90,7 +90,7 @@
 
 private:
     SkScalar fTextHeight;
-    SkAutoTUnref<const SkTextBlob> fBlob;
+    sk_sp<SkTextBlob> fBlob;
     typedef skiagm::GM INHERITED;
 };