The Tor Browser / file revision

 function testBug501690() {

     // Property cache assertion when 3 objects along a prototype chain have the same shape.

     function B(){}

     B.prototype = {x: 123};

     function D(){}

     D.prototype = new B;

     D.prototype.x = 1;    // [1] shapeOf(B.prototype) == shapeOf(D.prototype)

     arr = [new D, new D, new D, D.prototype];  // [2] all the same shape

     for (var i = 0; i < 4; i++)

         assertEq(arr[i].x, 1);  // same kshape [2], same vshape [1]

 }

 testBug501690();