diff -r 000000000000 -r 6474c204b198 toolkit/components/diskspacewatcher/nsIDiskSpaceWatcher.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/diskspacewatcher/nsIDiskSpaceWatcher.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,25 @@
+/* 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 "nsISupports.idl"
+
+%{ C++
+#ifdef XP_WIN
+#undef GetFreeSpace
+#endif
+%}
+
+[scriptable, uuid(3aceba74-2ed5-4e99-8fe4-06e90e2b8ef0)]
+interface nsIDiskSpaceWatcher : nsISupports
+{
+  readonly attribute bool isDiskFull; // True if we are low on disk space.
+  readonly attribute unsigned long long freeSpace; // The free space currently available.
+};
+
+%{ C++
+#define DISKSPACEWATCHER_CONTRACTID "@mozilla.org/toolkit/disk-space-watcher;1"
+
+// The data for this notification will be either 'free' or 'full'.
+#define DISKSPACEWATCHER_OBSERVER_TOPIC "disk-space-watcher"
+%}