The Tor Browser / file revision

 // After clearing one breakpoint, another breakpoint from a different Debugger object at the same instruction still works.

 function test(which) {

     var g = newGlobal();

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

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

            "    return " + which + ";\n" +  // line0 + 2

            "}\n");

     var log;

     var scripts = [];

     var handlers = [];

     function addDebugger(g, i) {

         var dbg = Debugger(g);

         dbg.onDebuggerStatement = function (frame) {

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

             scripts[i] = s;

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

             var handler = {hit: function (frame) { log += '' + i; } };

             s.setBreakpoint(0, handler);

             handlers[i] = handler;

         };

     }

     var expected = '';

     for (var i = 0; i < 3; i++) {

         addDebugger(g, i);

         if (i !== which)

             expected += '' + i;

     }

     g.eval('debugger;');

     for (var i = 0; i < 3; i++)

         assertEq(scripts[i].getBreakpoints()[0], handlers[i]);

     log = '';

     g.f();

     assertEq(log, '012');

     scripts[which].clearAllBreakpoints();

     log = '';

     g.f();

     assertEq(log, expected);

 }

 for (var j = 0; j < 3; j++)

     test(j);