diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug757199.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug757199.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,23 @@
+function ctor()
+{
+    this.a = 1;
+    this.b = 2;
+}
+function f2(o)
+{
+    o.c = 12;
+}
+function f()
+{
+    var x = new ctor();
+    verifyprebarriers();
+    f2(x);
+    verifyprebarriers();
+}
+f();
+f();
+var o = {};
+for (var i=0; i<1000; i++)
+    o['a'+i] = 3;
+f();
+f();