Fix layout test.

Author: savetheclocktower

test/unit/layout_test.js

@@ -86,7 +86,7 @@ new Test.Unit.Runner({
     this.assertEqual(13, layout.get('padding-bottom'), 'padding-right');
 
     // Ensure that we cleaned up after ourselves.
-    this.assert(!isDisplayed($('box3')), 'box should still be hidden');
+    this.assert(!isDisplayed($('box4')), 'box should still be hidden');
   },
 
   'test positioning on absolutely-positioned elements': function() {