The Tor Browser / file revision

 // frame.live is false for frames removed after their compartments stopped being debuggees.

 var g1 = newGlobal();

 var g2 = newGlobal();

 var dbg = Debugger(g1, g2);

 var hits = 0;

 var snapshot = [];

 dbg.onDebuggerStatement = function (frame) {

     if (hits++ === 0) {

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

     } else {

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

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

                 snapshot.push(f);

         }

         dbg.removeDebuggee(g2);

         return null;

     }

 };

 g1.eval("function z() { debugger; }");

 g2.z = g1.z;

 g2.eval("function y() { z(); }");

 g2.eval("function x() { y(); }");

 assertEq(g2.eval("debugger; 'ok';"), "ok");

 assertEq(hits, 2);

 assertEq(snapshot.length, 3);

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

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