diff -r 000000000000 -r 6474c204b198 mfbt/ChaosMode.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mfbt/ChaosMode.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,41 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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_ChaosMode_h
+#define mozilla_ChaosMode_h
+
+#include <stdint.h>
+#include <stdlib.h>
+
+namespace mozilla {
+
+/**
+ * When "chaos mode" is activated, code that makes implicitly nondeterministic
+ * choices is encouraged to make random and extreme choices, to test more
+ * code paths and uncover bugs.
+ */
+class ChaosMode
+{
+  public:
+    static bool isActive()
+    {
+      // Flip this to true to activate chaos mode
+      return false;
+    }
+
+    /**
+     * Returns a somewhat (but not uniformly) random uint32_t < aBound.
+     * Not to be used for anything except ChaosMode, since it's not very random.
+     */
+    static uint32_t randomUint32LessThan(uint32_t aBound)
+    {
+      return uint32_t(rand()) % aBound;
+    }
+};
+
+} /* namespace mozilla */
+
+#endif /* mozilla_ChaosMode_h */