Perf regression in polyfill - 20130808 release

[ebidel]

In Chrome stable (e.g. polyfill), toggle a feature. There's a 1-2 delay seconds under the latest release:
v20130808 latest: http://20130808.cr-status.appspot.com/features
v20130801 release: http://www.chromestatus.com/features

I did some experimenting and found that calling Platform.flush() helps
on mobile view (where the CSS transitions are disabled). There's no delay opening
a panel, but the tradeoff is that the color status flash in.

openChanged: function() {
  this.open ? this.classList.add('open') : this.classList.remove('open');
},
toggle: function(e, details, sender) {
   if (Platform.flags.shadow) {
     this.asyncMethod(function() {
       this.open = !this.open;
       Platform.flush(); 
     });
   } else {
     this.open = !this.open;
  }
}

Could all of this be from the new property reflection to attributes?

[ebidel]

Closing this. It's been addressed