diff -r 000000000000 -r 6474c204b198 xpcom/ds/nsIPropertyBag2.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/ds/nsIPropertyBag2.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,42 @@
+/* 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/. */
+
+/* nsIVariant based Property Bag support. */
+
+#include "nsIPropertyBag.idl"
+
+[scriptable, uuid(625cfd1e-da1e-4417-9ee9-dbc8e0b3fd79)]
+interface nsIPropertyBag2 : nsIPropertyBag
+{
+  // Accessing a property as a different type may attempt conversion to the
+  // requested value
+
+  int32_t     getPropertyAsInt32       (in AString prop);
+  uint32_t    getPropertyAsUint32      (in AString prop);
+  int64_t     getPropertyAsInt64       (in AString prop);
+  uint64_t    getPropertyAsUint64      (in AString prop);
+  double      getPropertyAsDouble      (in AString prop);
+  AString     getPropertyAsAString     (in AString prop);
+  ACString    getPropertyAsACString    (in AString prop);
+  AUTF8String getPropertyAsAUTF8String (in AString prop);
+  boolean     getPropertyAsBool        (in AString prop);
+
+  /**
+   * This method returns null if the value exists, but is null.
+   */
+  void        getPropertyAsInterface   (in AString prop,
+                                        in nsIIDRef iid,
+                                        [iid_is(iid), retval] out nsQIResult result);
+
+  /**
+   * This method returns null if the value does not exist,
+   * or exists but is null.
+   */
+  nsIVariant  get                      (in AString prop);
+ 
+  /**
+   * Check for the existence of a key.
+   */
+  boolean     hasKey                   (in AString prop);
+};