The Tor Browser / file revision

 // dbg.getNewestFrame in an onPop handler returns the frame being popped.

 var g = newGlobal();

 g.eval("function f() { debugger; }");

 g.eval("function g() { f(); }");

 g.eval("function h() { g(); }");

 g.eval("function i() { h(); }");

 var dbg = new Debugger(g);

 var log;

 dbg.onEnterFrame = function handleEnter(f) {

     log += "(" + f.callee.name;

     f.onPop = function handlePop(c) {

         log += ")" + f.callee.name;  

         assertEq(dbg.getNewestFrame(), this);

     };

 };

 log = '';

 g.i();

 assertEq(log, "(i(h(g(f)f)g)h)i");