The Tor Browser / file revision

 // The debugger can eval in any frame in the stack even if every frame was

 // pushed in a different context.

 var g = newGlobal();

 g.eval('function f(a) {\n' +

        '    if (a == 1)\n' +

        '        debugger;\n' +

        '    else\n' +

        '        evaluate("f(" + a + " - 1);", {newContext: true});\n' +

        '}\n');

 var N = 9;

 var dbg = new Debugger(g);

 var frames = [];

 var hits = 0;

 dbg.onEnterFrame = function (frame) {

     if (frame.type == "call" && frame.callee.name == "f") {

         frames.push(frame);

         frame.onPop = function () { assertEq(frames.pop(), frame); };

     }

 };

 dbg.onDebuggerStatement = function (frame) {

     assertEq(frames.length, N);

     var i = N;

     for (var f of frames)

         assertEq(f.eval('a').return, i--);

     hits++;

 };

 g.f(N);

 assertEq(hits, 1);

 assertEq(frames.length, 0);