The Tor Browser / file revision

 // frame.eval can evaluate code in a frame pushed in another context. Bug 749697.

 // In other words, the debugger can see all frames on the stack, even though

 // each frame is attached to a particular JSContext and multiple JSContexts may

 // have frames on the stack.

 var g = newGlobal();

 g.eval('function f(a) { debugger; evaluate("debugger;", {newContext: true}); }');

 var dbg = new Debugger(g);

 var hits = 0;

 dbg.onDebuggerStatement = function (frame1) {

     dbg.onDebuggerStatement = function (frame2) {

         assertEq(frame1.eval("a").return, 31);

         hits++;

     };

 };

 g.f(31);

 assertEq(hits, 1);