Proposal to fix very minor bug in disabling form field views.

Problematically, if you re-render a form field, the "isDisabled" attribute of the field remains as it was set, but when the field is redered it is never disabled. So, calling the disable() method on that field will do nothing. 

Here I suggest that you always set the disabled attribute if the element is not disabled. Not sure if this would cause any ripple effects (I suspect not) - and I am not sure you still need this part of the check: 
!this.isDisabled &&