Web Inspector: Console should do a better job of determining real constructor

[Joseph Pecoraro]

* SUMMARY
For Objects it is very useful to know the constructor. If the prototype has been modified and loses constructor the Console may show misleading values. We should do a better job here.

* TEST
<script>
function BottomLevel() { this._bottom = Math.random(); }
function TopLevel() { BottomLevel.call(this); this._top = Math.random(); }
TopLevel.prototype = {} // Comment this out to get desired result
TopLevel.prototype.__proto__ = BottomLevel.prototype;
var x = new TopLevel;
console.log(x); // => BottomLevel, because x.constructor => BottomLevel.
</script>

* STEPS TO REPRODUCE
1. Inspect test above
  => Console labels "x" a "BottomLevel" object
  => Expected to see "TopLevel" object, since that was the constructor

* NOTES
- Settings constructor on TopLevel fixes the issue
- Chrome shows "TopLevel" with/without prototype.constructor being set.

[Radar WebKit Bug Importer]

<rdar://problem/19281496>

[Radar WebKit Bug Importer]

<rdar://problem/19281616>