Oilpan: make DOMWindowProperty a GC mixin.

Source/core/frame/Screen.h

Index: Source/core/frame/Screen.h
diff --git a/Source/core/frame/Screen.h b/Source/core/frame/Screen.h
index bd91961acdf4500942d3c5f1b2a872a3516ccad4..af0f4213257f6f9f5fac1ad7fdb026560fa0ffd5 100644
--- a/Source/core/frame/Screen.h
+++ b/Source/core/frame/Screen.h
@@ -41,7 +41,7 @@ namespace blink {
 
 class LocalFrame;
 
-class Screen FINAL : public RefCountedWillBeGarbageCollectedFinalized<Screen>, public ScriptWrappable, public DOMWindowProperty, public WillBeHeapSupplementable<Screen> {
+class Screen FINAL : public RefCountedWillBeGarbageCollected<Screen>, public ScriptWrappable, public DOMWindowProperty, public WillBeHeapSupplementable<Screen> {
     DEFINE_WRAPPERTYPEINFO();
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Screen);
 public:
@@ -59,7 +59,7 @@ public:
     unsigned availHeight() const;
     unsigned availWidth() const;
 
-    void trace(Visitor*);
+    virtual void trace(Visitor*) OVERRIDE;
 
 private:
     explicit Screen(LocalFrame*);