Oilpan: Temporary fix for leaks through mapping from element to attribute node list.

Source/core/dom/Attr.h

Index: Source/core/dom/Attr.h
diff --git a/Source/core/dom/Attr.h b/Source/core/dom/Attr.h
index b6b2b4d362cf339423ffc2e85de3264af8852fae..36b715f60b09a0e055f2868fc3320ff3e9148fea 100644
--- a/Source/core/dom/Attr.h
+++ b/Source/core/dom/Attr.h
@@ -64,6 +64,7 @@ public:
     const AtomicString& prefix() const { return m_name.prefix(); }
 
     virtual void trace(Visitor*) OVERRIDE;
+    void clearWeakMembers(Visitor*);
 
 private:
     Attr(Element&, const QualifiedName&);
@@ -89,7 +90,13 @@ private:
 
     // Attr wraps either an element/name, or a name/value pair (when it's a standalone Node.)
     // Note that m_name is always set, but m_element/m_standaloneValue may be null.
-    RawPtrWillBeMember<Element> m_element;
+    //
+    // FIXME: Oilpan: m_element should be a Member. However, because of the
+    // current semantics of weak maps, we have to make it a WeakMember in order
+    // to not leak through the attrNodeListMap in Element.cpp. Once the semantics
+    // of weak maps has changed we should make this a Member and remove the custom
+    // weak processing.
+    RawPtrWillBeWeakMember<Element> m_element;
     QualifiedName m_name;
     // Holds the value if it is a standalone Node, or the local name of the
     // attribute it is attached to on an Element. The latter may (letter case)