diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/debug/Frame-eval-22.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/debug/Frame-eval-22.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,32 @@
+// Debugger.Frame preserves Ion frame identity
+
+load(libdir + "jitopts.js");
+
+if (!jitTogglesMatch(Opts_Ion2NoParallelCompilation))
+  quit();
+
+withJitOptions(Opts_Ion2NoParallelCompilation, function () {
+  var g = newGlobal();
+  var dbg1 = new Debugger;
+  var dbg2 = new Debugger;
+
+  g.toggle = function toggle(x, d) {
+    if (d) {
+      dbg1.addDebuggee(g);
+      dbg2.addDebuggee(g);
+      var frame1 = dbg1.getNewestFrame();
+      assertEq(frame1.environment.getVariable("x"), x);
+      assertEq(frame1.implementation, "ion");
+      frame1.environment.setVariable("x", "not 42");
+      assertEq(dbg2.getNewestFrame().environment.getVariable("x"), "not 42");
+    }
+  };
+
+  g.eval("" + function f(x, d) { toggle(x, d); });
+
+  g.eval("(" + function test() {
+    for (var i = 0; i < 5; i++)
+      f(42, false);
+    f(42, true);
+  } + ")();");
+});