guard rasterizer and drawlooper setters

tools/debugger/SkDrawCommand.cpp

Index: tools/debugger/SkDrawCommand.cpp
diff --git a/tools/debugger/SkDrawCommand.cpp b/tools/debugger/SkDrawCommand.cpp
index ab9c9de53c5114b3cc5159216c025543bc2f5350..45c9ffe0cad6e390e62e0681e309c85bc56a5c60 100644
--- a/tools/debugger/SkDrawCommand.cpp
+++ b/tools/debugger/SkDrawCommand.cpp
@@ -1155,10 +1155,9 @@ static void extract_json_paint_looper(Json::Value& jsonPaint, UrlDataManager& ur
                                       SkPaint* target) {
     if (jsonPaint.isMember(SKDEBUGCANVAS_ATTRIBUTE_LOOPER)) {
         Json::Value jsonLooper = jsonPaint[SKDEBUGCANVAS_ATTRIBUTE_LOOPER];
-        SkDrawLooper* looper = (SkDrawLooper*) load_flattenable(jsonLooper, urlDataManager);
+        sk_sp<SkDrawLooper> looper((SkDrawLooper*) load_flattenable(jsonLooper, urlDataManager));
         if (looper != nullptr) {
-            target->setLooper(looper);
-            looper->unref();
+            target->setLooper(std::move(looper));
         }
     }
 }