record drawfilters

gm/drawfilter.cpp

Index: gm/drawfilter.cpp
diff --git a/gm/drawfilter.cpp b/gm/drawfilter.cpp
index 33e1d0085352125cd77a3af44d86949965a1ee93..d989c4ccecda2c86529eef54e8a2df34f29e68a8 100644
--- a/gm/drawfilter.cpp
+++ b/gm/drawfilter.cpp
@@ -57,12 +57,9 @@ protected:
         SkRect r = { 20, 20, 100, 100 };
         canvas->setDrawFilter(nullptr);
         canvas->drawRect(r, p);
-        TestFilter redNoBlur;
-        canvas->setDrawFilter(&redNoBlur);
+        canvas->setDrawFilter(new TestFilter)->unref();
         canvas->translate(120.0f, 40.0f);
         canvas->drawRect(r, p);
-
-        // Must unset if the DrawFilter is from the stack to avoid refcount errors!
         canvas->setDrawFilter(nullptr);
     }