Implemented XMLSerializer in PrivateScript.

Source/core/xml/DocumentXMLSerializer.idl

Index: Source/core/xml/DocumentXMLSerializer.idl
diff --git a/Source/core/xml/DocumentXMLSerializer.idl b/Source/core/xml/DocumentXMLSerializer.idl
new file mode 100644
index 0000000000000000000000000000000000000000..5409bb6489962813b6190503fd0eb5af4a0e08e3
--- /dev/null
+++ b/Source/core/xml/DocumentXMLSerializer.idl
@@ -0,0 +1,8 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+partial interface Document {
+    [OnlyExposedToPrivateScript] readonly attribute boolean hasXMLDeclaration;

[yosin_UTC9, 2014/09/03 03:35:01]

Can we pass them as arguments for JS XML serializer?

This means we still keep C++ XMLSerializer::serializeToString() and it calls
BlinkInJS.

String XMLSerializer::serializeToString(...) {
  String result;
  V8XMLSerializer::serializeToStringInJavaScript(..., hasXMLDeclaration,
isXMLStandaloneSpecified);
  return result;
}

+    [OnlyExposedToPrivateScript] readonly attribute boolean isXMLStandaloneSpecified;
+};