guard rasterizer and drawlooper setters

Need to land https://codereview.chromium.org/1823513002/ first

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1821533002

Review URL: https://codereview.chromium.org/1821533002
diff --git a/samplecode/SampleFilterFuzz.cpp b/samplecode/SampleFilterFuzz.cpp
index fe2fb0b..dd0fa40 100644
--- a/samplecode/SampleFilterFuzz.cpp
+++ b/samplecode/SampleFilterFuzz.cpp
@@ -536,8 +536,7 @@
         paintForRasterizer = make_paint();
     }
     rasterizerBuilder.addLayer(paintForRasterizer);
-    SkAutoTUnref<SkRasterizer> rasterizer(rasterizerBuilder.detachRasterizer());
-    paint.setRasterizer(rasterizer);
+    paint.setRasterizer(rasterizerBuilder.detach());
     paint.setImageFilter(make_image_filter());
     SkAutoDataUnref data(make_3Dlut(nullptr, make_bool(), make_bool(), make_bool()));
     paint.setTextAlign(make_paint_align());