diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8/extensions/regress-394709.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8/extensions/regress-394709.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,60 @@
+/* -*- 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/. */
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 394709;
+var summary = 'Do not leak with object.watch and closure';
+var actual = 'No Leak';
+var expect = 'No Leak';
+
+if (typeof countHeap == 'undefined')
+{
+  countHeap = function () { 
+    print('This test requires countHeap which is not supported'); 
+    return 0;
+  };
+}
+
+//-----------------------------------------------------------------------------
+test();
+//-----------------------------------------------------------------------------
+
+function test()
+{
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+
+  // Ensure that we flush all values so that gc() collects all objects that
+  // the user cannot reach from JS.
+  eval();
+
+  runtest();
+  gc();
+  var count1 = countHeap();
+  runtest();
+  gc();
+  var count2 = countHeap();
+  runtest();
+  gc();
+  var count3 = countHeap();
+  /* Try to be tolerant of conservative GC noise: we want a steady leak. */
+  if (count1 < count2 && count2 < count3)
+    throw "A leaky watch point is detected";
+
+  function runtest () {
+    var obj = { b: 0 };
+    obj.watch('b', watcher);
+
+    function watcher(id, old, value) {
+      ++obj.n;
+      return value;
+    }
+  }
+
+  reportCompare(expect, actual, summary);
+
+  exitFunc ('test');
+}