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/SampleUnpremul.cpp b/samplecode/SampleUnpremul.cpp
index fb9735c..919fb64 100644
--- a/samplecode/SampleUnpremul.cpp
+++ b/samplecode/SampleUnpremul.cpp
@@ -80,10 +80,9 @@
         SkPaint paint;
         paint.setAntiAlias(true);
         paint.setTextSize(SkIntToScalar(24));
-        SkAutoTUnref<SkDrawLooper> looper(
-            SkBlurDrawLooper::Create(SK_ColorBLUE,
-                                     SkBlurMask::ConvertRadiusToSigma(SkIntToScalar(2)),
-                                     0, 0));
+        auto looper(
+            SkBlurDrawLooper::Make(SK_ColorBLUE, SkBlurMask::ConvertRadiusToSigma(SkIntToScalar(2)),
+                                   0, 0));
         paint.setLooper(looper);
         SkScalar height = paint.getFontMetrics(nullptr);
         if (!fDecodeSucceeded) {