Oilpan: move LiveNodeList collections to the heap.

Source/core/html/LabelableElement.h

Index: Source/core/html/LabelableElement.h
diff --git a/Source/core/html/LabelableElement.h b/Source/core/html/LabelableElement.h
index ed9f62a8072559a77f17069b15aa86b61531e302..59b3ccf4efe407720ed969972b081153423e4594 100644
--- a/Source/core/html/LabelableElement.h
+++ b/Source/core/html/LabelableElement.h
@@ -40,7 +40,7 @@ namespace WebCore {
 class LabelableElement : public HTMLElement {
 public:
     virtual ~LabelableElement();
-    PassRefPtr<NodeList> labels();
+    PassRefPtrWillBeRawPtr<NodeList> labels();
     virtual bool supportLabels() const { return false; }
 
     virtual void trace(Visitor*) OVERRIDE;