Implemented XMLSerializer in PrivateScript.

Source/core/xml/XMLSerializer.h

Index: Source/core/xml/XMLSerializer.h
diff --git a/Source/core/xml/XMLSerializer.h b/Source/core/xml/XMLSerializer.h
index 38b3131d034b78981c7a1c439eddb51fe9b9d448..81ad81725ed8c04356c9b7f404a41ab9b4537aa4 100644
--- a/Source/core/xml/XMLSerializer.h
+++ b/Source/core/xml/XMLSerializer.h
@@ -28,15 +28,16 @@
 
 namespace blink {
 
+class Document;
 class ExceptionState;
 class Node;
 
 class XMLSerializer final : public RefCountedWillBeGarbageCollected<XMLSerializer>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static PassRefPtrWillBeRawPtr<XMLSerializer> create()
+    static PassRefPtrWillBeRawPtr<XMLSerializer> create(Document& document)
     {
-        return adoptRefWillBeNoop(new XMLSerializer);
+        return adoptRefWillBeNoop(new XMLSerializer(document));
     }
 
     String serializeToString(Node*, ExceptionState&);
@@ -44,7 +45,11 @@ public:
     void trace(Visitor*) { }
 
 private:
-    XMLSerializer() { }
+    XMLSerializer(Document& document)
+        : m_document(&document)
+    { }
+
+    RefPtrWillBeMember<Document> m_document;
 };
 
 } // namespace blink