The Tor Browser / file revision

 // frame.live is false for frames discarded during uncatchable error unwinding.

 var g = newGlobal();

 var dbg = Debugger(g);

 var hits = 0;

 var snapshot;

 dbg.onDebuggerStatement = function (frame) {

     var stack = [];

     for (var f = frame; f; f = f.older) {

         if (f.type === "call" && f.script !== null)

             stack.push(f);

     }

     snapshot = stack;

     if (hits++ === 0)

         assertEq(frame.eval("x();"), null);

     else

         return null;

 };

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

 g.eval("function y() { z(); }");

 g.eval("function x() { y(); }");

 assertEq(g.eval("debugger; 'ok';"), "ok");

 assertEq(hits, 2);

 assertEq(snapshot.length, 3);

 for (var i = 0; i < snapshot.length; i++)

     assertEq(snapshot[i].live, false);