Warning: event.returnValue is deprecated

[mahboob-awan]

event.returnValue is used at following place:
https://github.com/facebook/react/blob/master/src/event/synthetic/SyntheticEvent.js#L82

So getting this warning at Chrome [Version 31.0.1650.48] :

 event.returnValue is deprecated. Please use the standard event.preventDefault() instead.[react.js:11173]

You may notice that same issue is reported at:
http://bugs.jquery.com/ticket/14320
angular/angular.js#4557

So, kindly update code to avoid this Warning. Thanks

[sophiebits]

Dupe of #527.