The Tor Browser / file revision

 // getLineOffsets works with instructions reachable only by breaking out of a loop or switch.

 var g = newGlobal();

 g.line0 = null;

 var dbg = Debugger(g);

 var where;

 dbg.onDebuggerStatement = function (frame) {

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

     var lineno = g.line0 + where;

     var offs = s.getLineOffsets(lineno);

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

         assertEq(s.getOffsetLine(offs[i]), lineno);

         s.setBreakpoint(offs[i], {hit: function () { g.log += 'B'; }});

     }

     g.log += 'A';

 };

 function test(s) {

     var count = (s.split(/\n/).length - 1); // number of newlines in s

     g.log = '';

     where = 3 + count + 1;

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

            "debugger;\n" +          // line0 + 1

            "function f(i) {\n" +    // line0 + 2

            s +                      // line0 + 3 ... line0 + where - 2

            "    log += '?';\n" +    // line0 + where - 1

            "    log += '!';\n" +    // line0 + where

            "}\n");

     g.f(0);

     assertEq(g.log, 'A?B!');

 }

 test("i = 128;\n" +

      "for (;;) {\n" +

      "    var x = i - 10;;\n" +

      "    if (x < 0)\n" +

      "        break;\n" +

      "    i >>= 2;\n" +

      "}\n");

 test("while (true)\n" +

      "    if (++i === 2) break;\n");

 test("do {\n" +

      "    if (++i === 2) break;\n" +

      "} while (true);\n");

 test("switch (i) {\n" +

      "  case 2: return 7;\n" +

      "  case 1: return 8;\n" +

      "  case 0: break;\n" +

      "  default: return -i;\n" +

      "}\n");