diff -r 000000000000 -r 6474c204b198 dom/interfaces/json/nsIJSON.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/interfaces/json/nsIJSON.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "domstubs.idl"
+
+interface nsIInputStream;
+interface nsIOutputStream;
+interface nsIScriptGlobalObject;
+
+[ptr] native JSValPtr(JS::Value);
+[ptr] native JSContext(JSContext);
+
+%{C++
+#include "js/TypeDecls.h"
+%}
+
+/**
+ * Don't use this!  Use JSON.parse and JSON.stringify directly.
+ */
+[scriptable, uuid(083aebb0-7790-43b2-ae81-9e404e626236)]
+interface nsIJSON : nsISupports
+{
+  /**
+   * New users should use JSON.stringify!
+   * The encode() method is only present for backward compatibility.
+   * encode() is not a conforming JSON stringify implementation!
+   */
+  [deprecated,implicit_jscontext,optional_argc]
+  AString encode([optional] in jsval value);
+
+  /**
+   * New users should use JSON.stringify.
+   * You may also want to have a look at nsIConverterOutputStream.
+   *
+   * The encodeToStream() method is only present for backward compatibility.
+   * encodeToStream() is not a conforming JSON stringify implementation!
+   */
+  [deprecated,implicit_jscontext,optional_argc]
+  void encodeToStream(in nsIOutputStream stream,
+                      in string charset,
+                      in boolean writeBOM,
+                      [optional] in jsval value);
+
+  /**
+   * New users should use JSON.parse!
+   * The decode() method is only present for backward compatibility.
+   */
+  [deprecated,implicit_jscontext]
+  jsval decode(in AString str);
+
+  [implicit_jscontext]
+  jsval decodeFromStream(in nsIInputStream stream,
+                         in long contentLength);
+
+  [noscript] AString  encodeFromJSVal(in JSValPtr value, in JSContext cx);
+
+  // Make sure you GCroot the result of this function before using it.
+  [noscript] jsval    decodeToJSVal(in AString str, in JSContext cx);
+};