Oilpan: add Element/Node Member fields to stack allocated objects.

Source/core/dom/PositionIterator.h

Index: Source/core/dom/PositionIterator.h
diff --git a/Source/core/dom/PositionIterator.h b/Source/core/dom/PositionIterator.h
index 4d81cd1de3364324a16c8d394d4d80299265a071..b3bcba0a0d0c4d79f04dea119403d39fe2d5ff37 100644
--- a/Source/core/dom/PositionIterator.h
+++ b/Source/core/dom/PositionIterator.h
@@ -35,10 +35,11 @@ namespace WebCore {
 // increment, decrement, and several predicates on the Position it is at.
 // Conversion to/from Position is O(n) in the offset.
 class PositionIterator {
+    STACK_ALLOCATED();
 public:
     PositionIterator()
-        : m_anchorNode(0)
-        , m_nodeAfterPositionInAnchor(0)
+        : m_anchorNode(nullptr)
+        , m_nodeAfterPositionInAnchor(nullptr)
         , m_offsetInAnchor(0)
     {
     }
@@ -64,8 +65,8 @@ public:
     bool isCandidate() const;
 
 private:
-    Node* m_anchorNode;
-    Node* m_nodeAfterPositionInAnchor; // If this is non-null, m_nodeAfterPositionInAnchor->parentNode() == m_anchorNode;
+    RawPtrWillBeMember<Node> m_anchorNode;
+    RawPtrWillBeMember<Node> m_nodeAfterPositionInAnchor; // If this is non-null, m_nodeAfterPositionInAnchor->parentNode() == m_anchorNode;
     int m_offsetInAnchor;
 };