[oilpan]: Move DOMWindowCSS to the oilpan heap using transition types.

Source/core/css/DOMWindowCSS.h

Index: Source/core/css/DOMWindowCSS.h
diff --git a/Source/core/css/DOMWindowCSS.h b/Source/core/css/DOMWindowCSS.h
index e6c6d19b2dcfb39381a6f82f5c4ddc388ef5d142..3d845bbfb9e452d6cac2c625d2bdfd2c5dfc34fe 100644
--- a/Source/core/css/DOMWindowCSS.h
+++ b/Source/core/css/DOMWindowCSS.h
@@ -30,19 +30,22 @@
 #ifndef DOMWindowCSS_h
 #define DOMWindowCSS_h
 
+#include "heap/Handle.h"
 #include "wtf/Forward.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 
 namespace WebCore {
 
-class DOMWindowCSS : public RefCounted<DOMWindowCSS> {
+class DOMWindowCSS : public RefCountedWillBeGarbageCollected<DOMWindowCSS> {
 public:
-    static PassRefPtr<DOMWindowCSS> create();
+    static PassRefPtrWillBeRawPtr<DOMWindowCSS> create();
 
     bool supports(const String& property, const String& value) const;
     bool supports(const String& conditionText) const;
 
+    void trace(Visitor*) { }
+
 private:
     DOMWindowCSS()
     {