The Tor Browser / file revision

 // frame.environment is different for different activations of a scope.

 var g = newGlobal();

 var dbg = Debugger(g);

 g.eval("function h() { debugger; }");

 var arr;

 dbg.onDebuggerStatement = function (hframe) {

     var e = hframe.older.environment;

     assertEq(arr.indexOf(e), -1);

     arr.push(e);

 };

 function test(code, expectedHits) {

     arr = [];

     g.eval(code);

     assertEq(arr.length, expectedHits);

 }

 // two separate calls to a function

 test("(function () { var f = function (a) { h(); return a; }; f(1); f(2); })();", 2);

 // recursive calls to a function

 test("(function f(n) { h(); return n < 2 ? 1 : n * f(n - 1); })(3);", 3);

 // separate visits to a block in the same call frame

 test("(function () { for (var i = 0; i < 3; i++) { let j = i * 4; h(); }})();", 3);

 // two strict direct eval calls in the same function scope

 test("(function () { 'use strict'; for (var i = 0; i < 3; i++) eval('h();'); })();", 3);