The Tor Browser / file revision

 // A breakpoint handler hit method can return {return: val} to force the frame to return.

 var g = newGlobal();

 var dbg = Debugger(g);

 dbg.onDebuggerStatement = function (frame) {

     g.log += 'D';

     function hit(frame) {

         g.log += 'H';

         return {return: 'ok'};

     }

     var f = frame.eval("f").return;

     var s = f.script;

     var offs = s.getLineOffsets(g.line0 + 2);

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

         s.setBreakpoint(offs[i], {hit: hit});

     var rv = f.call();

     assertEq(rv.return, 'ok');

     g.log += 'X';

 };

 g.log = '';

 g.eval("line0 = Error().lineNumber;\n" +

        "function f() {\n" +     // line0 + 1

        "    log += '2';\n" +    // line0 + 2

        "}\n" +

        "debugger;\n");

 assertEq(g.log, 'DHX');