Provides an easy way to toggle a checkbox input's special 'indeterminate' property. This is a visual toggle only and in no way affects the model or value outside of native browser behavior at this time.
value = {{value|json}}
isKnown = {{isKnown|json}}
Convenience.
Indeterminate: <input type="checkbox" ui-indeterminate="isKnown" readonly>
Toggle indeterminate here: <input type="checkbox" ng-model="isKnown">