Oilpan: move DOM string collection objects to the Oilpan heap.

Source/core/html/HTMLLinkElement.h

Index: Source/core/html/HTMLLinkElement.h
diff --git a/Source/core/html/HTMLLinkElement.h b/Source/core/html/HTMLLinkElement.h
index 7ae3cbee6900b3073dedf16c43088503eca01413..becb032bbd581677eaec3e49a48f120ccb0d792e 100644
--- a/Source/core/html/HTMLLinkElement.h
+++ b/Source/core/html/HTMLLinkElement.h
@@ -195,6 +195,8 @@ private:
     virtual void didSendLoadForLinkPrerender() OVERRIDE;
     virtual void didSendDOMContentLoadedForLinkPrerender() OVERRIDE;
 
+    virtual void trace(Visitor*) OVERRIDE;
+
 private:
     HTMLLinkElement(Document&, bool createdByParser);
 
@@ -203,7 +205,7 @@ private:
 
     String m_type;
     String m_media;
-    RefPtr<DOMSettableTokenList> m_sizes;
+    RefPtrWillBeMember<DOMSettableTokenList> m_sizes;
     Vector<IntSize> m_iconSizes;
     LinkRelAttribute m_relAttribute;