diff -r 000000000000 -r 6474c204b198 content/xml/document/src/nsXMLPrettyPrinter.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/xml/document/src/nsXMLPrettyPrinter.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,58 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsXMLPrettyPrinter_h__
+#define nsXMLPrettyPrinter_h__
+
+#include "nsStubDocumentObserver.h"
+#include "nsCOMPtr.h"
+
+class nsIDocument;
+
+class nsXMLPrettyPrinter : public nsStubDocumentObserver
+{
+public:
+    nsXMLPrettyPrinter();
+    virtual ~nsXMLPrettyPrinter();
+
+    NS_DECL_ISUPPORTS
+
+    // nsIMutationObserver
+    NS_DECL_NSIMUTATIONOBSERVER_ATTRIBUTECHANGED
+    NS_DECL_NSIMUTATIONOBSERVER_CONTENTAPPENDED
+    NS_DECL_NSIMUTATIONOBSERVER_CONTENTINSERTED
+    NS_DECL_NSIMUTATIONOBSERVER_CONTENTREMOVED
+    NS_DECL_NSIMUTATIONOBSERVER_NODEWILLBEDESTROYED
+
+    /**
+     * This will prettyprint the document if the document is loaded in a
+     * displayed window.
+     *
+     * @param aDocument  document to prettyprint
+     * @param [out] aDidPrettyPrint if true, and error not returned, actually
+     *              went ahead with prettyprinting the document.
+     */
+    nsresult PrettyPrint(nsIDocument* aDocument, bool* aDidPrettyPrint);
+
+    /**
+     * Unhook the prettyprinter
+     */
+    void Unhook();
+private:
+    /**
+     * Signals for unhooking by setting mUnhookPending if the node changed is
+     * non-anonymous content.
+     *
+     * @param aContent  content that has changed
+     */
+    void MaybeUnhook(nsIContent* aContent);
+
+    nsIDocument* mDocument; //weak. Set as long as we're observing the document
+    bool mUnhookPending;
+};
+
+nsresult NS_NewXMLPrettyPrinter(nsXMLPrettyPrinter** aPrinter);
+
+#endif //nsXMLPrettyPrinter_h__