Oilpan: Prepare moving AXObject to heap

Source/modules/accessibility/AXImageMapLink.h

Index: Source/modules/accessibility/AXImageMapLink.h
diff --git a/Source/modules/accessibility/AXImageMapLink.h b/Source/modules/accessibility/AXImageMapLink.h
index 87f1310935cb39076d97d3579db889980d18d1f5..72b8e823367e0dbc0adc5f083d92742d5a712b9d 100644
--- a/Source/modules/accessibility/AXImageMapLink.h
+++ b/Source/modules/accessibility/AXImageMapLink.h
@@ -43,8 +43,9 @@ private:
     explicit AXImageMapLink(AXObjectCacheImpl&);
 
 public:
-    static PassRefPtr<AXImageMapLink> create(AXObjectCacheImpl&);
+    static PassRefPtrWillBeRawPtr<AXImageMapLink> create(AXObjectCacheImpl&);
     virtual ~AXImageMapLink();
+    DECLARE_VIRTUAL_TRACE();
 
     void setHTMLAreaElement(HTMLAreaElement* element) { m_areaElement = element; }
     HTMLAreaElement* areaElement() const { return m_areaElement.get(); }
@@ -69,8 +70,8 @@ public:
     virtual LayoutRect elementRect() const override;
 
 private:
-    RefPtrWillBePersistent<HTMLAreaElement> m_areaElement;
-    RefPtrWillBePersistent<HTMLMapElement> m_mapElement;
+    RefPtrWillBeWeakMember<HTMLAreaElement> m_areaElement;
+    RefPtrWillBeWeakMember<HTMLMapElement> m_mapElement;
 
     virtual void detachFromParent() override;