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/samplecode/SampleFatBits.cpp b/samplecode/SampleFatBits.cpp
index 4b15e37..dd58881 100644
--- a/samplecode/SampleFatBits.cpp
+++ b/samplecode/SampleFatBits.cpp
@@ -91,9 +91,9 @@
         fShader = sk_tool_utils::create_checkerboard_shader(0xFFCCCCCC, 0xFFFFFFFF, zoom);
 
         SkImageInfo info = SkImageInfo::MakeN32Premul(width, height);
-        fMinSurface.reset(SkSurface::NewRaster(info));
+        fMinSurface = SkSurface::MakeRaster(info);
         info = info.makeWH(width * zoom, height * zoom);
-        fMaxSurface.reset(SkSurface::NewRaster(info));
+        fMaxSurface = SkSurface::MakeRaster(info);
     }
 
     void drawBG(SkCanvas*);
@@ -111,8 +111,8 @@
     SkMatrix fMatrix, fInverse;
     SkRect   fBounds, fClipRect;
     sk_sp<SkShader> fShader;
-    SkAutoTUnref<SkSurface> fMinSurface;
-    SkAutoTUnref<SkSurface> fMaxSurface;
+    sk_sp<SkSurface> fMinSurface;
+    sk_sp<SkSurface> fMaxSurface;
 
     void setupPaint(SkPaint* paint) {
         bool aa = this->getAA();
@@ -162,7 +162,7 @@
     }
 
     void copyMinToMax() {
-        erase(fMaxSurface);
+        erase(fMaxSurface.get());
         SkCanvas* canvas = fMaxSurface->getCanvas();
         canvas->save();
         canvas->concat(fMatrix);
@@ -275,7 +275,7 @@
         apply_grid(pts, 2);
     }
 
-    erase(fMinSurface);
+    erase(fMinSurface.get());
     this->setupPaint(&paint);
     paint.setColor(FAT_PIXEL_COLOR);
     if (fUseClip) {
@@ -310,7 +310,7 @@
     SkRect r;
     r.set(pts, 2);
 
-    erase(fMinSurface);
+    erase(fMinSurface.get());
     this->setupPaint(&paint);
     paint.setColor(FAT_PIXEL_COLOR);
     {
@@ -356,7 +356,7 @@
     path.lineTo(pts[2]);
     path.close();
 
-    erase(fMinSurface);
+    erase(fMinSurface.get());
     this->setupPaint(&paint);
     paint.setColor(FAT_PIXEL_COLOR);
     fMinSurface->getCanvas()->drawPath(path, paint);