diff -r 000000000000 -r 6474c204b198 js/src/jsapi-tests/testAddPropertyPropcache.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jsapi-tests/testAddPropertyPropcache.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,74 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ */
+/* 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 "jsapi-tests/tests.h"
+
+static int callCount = 0;
+
+static bool
+AddProperty(JSContext *cx, JS::HandleObject obj, JS::HandleId id, JS::MutableHandleValue vp)
+{
+    callCount++;
+    return true;
+}
+
+static const JSClass AddPropertyClass = {
+    "AddPropertyTester",
+    0,
+    AddProperty,
+    JS_DeletePropertyStub,   /* delProperty */
+    JS_PropertyStub,         /* getProperty */
+    JS_StrictPropertyStub,   /* setProperty */
+    JS_EnumerateStub,
+    JS_ResolveStub,
+    JS_ConvertStub
+};
+
+BEGIN_TEST(testAddPropertyHook)
+{
+    /*
+     * Do the test a bunch of times, because sometimes we seem to randomly
+     * miss the propcache.
+     */
+    static const int ExpectedCount = 100;
+
+    JS::RootedObject obj(cx, JS_NewObject(cx, nullptr, JS::NullPtr(), JS::NullPtr()));
+    CHECK(obj);
+    JS::RootedValue proto(cx, OBJECT_TO_JSVAL(obj));
+    JS_InitClass(cx, global, obj, &AddPropertyClass, nullptr, 0, nullptr, nullptr, nullptr,
+                 nullptr);
+
+    obj = JS_NewArrayObject(cx, 0);
+    CHECK(obj);
+    JS::RootedValue arr(cx, OBJECT_TO_JSVAL(obj));
+
+    CHECK(JS_DefineProperty(cx, global, "arr", arr, JSPROP_ENUMERATE,
+                            JS_PropertyStub, JS_StrictPropertyStub));
+
+    for (int i = 0; i < ExpectedCount; ++i) {
+        obj = JS_NewObject(cx, &AddPropertyClass, JS::NullPtr(), JS::NullPtr());
+        CHECK(obj);
+        JS::RootedValue vobj(cx, OBJECT_TO_JSVAL(obj));
+        JS::RootedObject arrObj(cx, JSVAL_TO_OBJECT(arr));
+        CHECK(JS_DefineElement(cx, arrObj, i, vobj,
+                               JS_PropertyStub, JS_StrictPropertyStub,
+                               JSPROP_ENUMERATE));
+    }
+
+    // Now add a prop to each of the objects, but make sure to do
+    // so at the same bytecode location so we can hit the propcache.
+    EXEC("'use strict';                                     \n"
+         "for (var i = 0; i < arr.length; ++i)              \n"
+         "  arr[i].prop = 42;                               \n"
+         );
+
+    CHECK(callCount == ExpectedCount);
+
+    return true;
+}
+END_TEST(testAddPropertyHook)
+