diff -r 000000000000 -r 6474c204b198 xpcom/threads/HangMonitor.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/threads/HangMonitor.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,54 @@
+/* -*- Mode: C++; tab-width: 8; 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/. */
+
+#ifndef mozilla_HangMonitor_h
+#define mozilla_HangMonitor_h
+
+namespace mozilla { namespace HangMonitor {
+
+/**
+ * Signifies the type of activity in question
+*/
+enum ActivityType {
+  /* There is activity and it is known to be UI related activity. */
+  kUIActivity,
+
+  /* There is non UI activity and no UI activity is pending */
+  kActivityNoUIAVail,
+
+  /* There is non UI activity and UI activity is known to be pending */
+  kActivityUIAVail,
+
+  /* There is non UI activity and UI activity pending is unknown */
+  kGeneralActivity
+};
+
+/**
+ * Start monitoring hangs. Should be called by the XPCOM startup process only.
+ */
+void Startup();
+
+/**
+ * Stop monitoring hangs and join the thread.
+ */
+void Shutdown();
+
+/**
+ * Notify the hang monitor of activity which will reset its internal timer.
+ * 
+ * @param activityType The type of activity being reported.
+ * @see ActivityType
+ */
+void NotifyActivity(ActivityType activityType = kGeneralActivity);
+
+/*
+ * Notify the hang monitor that the browser is now idle and no detection should
+ * be done.
+ */
+void Suspend();
+
+} } // namespace mozilla::HangMonitor
+
+#endif // mozilla_HangMonitor_h