switch surface to sk_sp

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1817383002
CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-x86_64-Release-CMake-Trybot,Build-Mac-Clang-x86_64-Release-CMake-Trybot

Review URL: https://codereview.chromium.org/1817383002
diff --git a/gm/transparency.cpp b/gm/transparency.cpp
index 5e05761..5f32460 100644
--- a/gm/transparency.cpp
+++ b/gm/transparency.cpp
@@ -62,7 +62,7 @@
             sk_tool_utils::color_to_565(0xFF666666), 8);
     {
         SkAutoCanvasRestore autoCanvasRestore(canvas, true);
-        SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterN32Premul(256, 9));
+        auto surface(SkSurface::MakeRasterN32Premul(256, 9));
         make_transparency(surface->getCanvas(), 256.0f, 9.0f);
         canvas->scale(7.0f, 120.0f);
         surface->draw(canvas, 0, 0, nullptr);