[oilpan] The Node hierarchy should have correct accept method chains

Source/core/dom/Entity.h

Index: Source/core/dom/Entity.h
diff --git a/Source/core/dom/Entity.h b/Source/core/dom/Entity.h
index d8535f4779cdd73ec4a624e97152347d1cb15f5c..68a996c4126271cf325d191235a2d057f33d1f7c 100644
--- a/Source/core/dom/Entity.h
+++ b/Source/core/dom/Entity.h
@@ -33,6 +33,11 @@ public:
     String systemId() const { ASSERT_NOT_REACHED(); return String(); }
     String notationName() const { ASSERT_NOT_REACHED(); return String(); }
 
+    void acceptHeapVisitor(Visitor* visitor) const OVERRIDE
+    {
+        ContainerNode::acceptHeapVisitor(visitor);
+    }
+
 private:
     Entity() : ContainerNode(nullptr)
     {