GC plugin: RefPtr<T> is legal if T is RefCountedGC-derived.

tools/clang/blink_gc_plugin/tests/heap/stubs.h

Index: tools/clang/blink_gc_plugin/tests/heap/stubs.h
diff --git a/tools/clang/blink_gc_plugin/tests/heap/stubs.h b/tools/clang/blink_gc_plugin/tests/heap/stubs.h
index 5e07c2366e05cacfc3f874c8fdc03eb25517c6ab..a31ef3abeed309974308f1e39bfa080680bfea07 100644
--- a/tools/clang/blink_gc_plugin/tests/heap/stubs.h
+++ b/tools/clang/blink_gc_plugin/tests/heap/stubs.h
@@ -154,6 +154,9 @@ template<typename T> class GarbageCollected { };
 template<typename T>
 class GarbageCollectedFinalized : public GarbageCollected<T> { };
 
+template<typename T>
+class RefCountedGarbageCollected : public GarbageCollectedFinalized<T> { };
+
 template<typename T> class Member {
 public:
     operator T*() const { return 0; }