Oilpan: move LiveNodeList collections to the heap.

Source/core/html/LabelableElement.cpp

Index: Source/core/html/LabelableElement.cpp
diff --git a/Source/core/html/LabelableElement.cpp b/Source/core/html/LabelableElement.cpp
index 18cfa097a53d8c1af8cb56ac591f5189dc9ca1eb..cb34468bf4ca42084142e6e3c9fd72fd9c7f90cd 100644
--- a/Source/core/html/LabelableElement.cpp
+++ b/Source/core/html/LabelableElement.cpp
@@ -39,7 +39,7 @@ LabelableElement::~LabelableElement()
 {
 }
 
-PassRefPtr<NodeList> LabelableElement::labels()
+PassRefPtrWillBeRawPtr<NodeList> LabelableElement::labels()
 {
     if (!supportLabels())
         return nullptr;