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 // onPop surfaces.

 load(libdir + "asserts.js");

 var g = newGlobal();

 var dbg = new Debugger(g);

 // Assigning a bogus value to Debugger.Frame.prototype.onPop raises a TypeError.

 function test(badValue) {

     print("store " + uneval(badValue) + " in Debugger.Frame.prototype.onPop");

     var log;

     dbg.onDebuggerStatement = function handleDebugger(frame) {

         log += "d";

         assertThrowsInstanceOf(function () { frame.onPop = badValue; }, TypeError);

     };

     log = "";

     g.eval("debugger");

     assertEq(log, "d");

 }

 test(null);

 test(false);

 test(1);

 test("stringy");

 test({});

 test([]);

 // Getting and setting the prototype's onPop is an error.

 assertThrowsInstanceOf(function () { Debugger.Frame.prototype.onPop; }, TypeError);

 assertThrowsInstanceOf(

     function () { Debugger.Frame.prototype.onPop = function () {}; },

     TypeError);

 // The getters and setters correctly check the type of their 'this' argument.

 var descriptor = Object.getOwnPropertyDescriptor(Debugger.Frame.prototype, 'onPop');

 assertEq(descriptor.configurable, true);

 assertEq(descriptor.enumerable, false);

 assertThrowsInstanceOf(function () { descriptor.get.call({}); }, TypeError);

 assertThrowsInstanceOf(function () { descriptor.set.call({}, function() {}); }, TypeError);