Mixed Checkbox Example: update individual checkbox states when master…

… is mixed (pull #491)

Fix issue #486 by adding a procedure to update individual checkbox states when master is mixed.

examples/checkbox/checkbox-2/js/checkboxMixed.js

@@ -67,10 +67,17 @@ CheckboxMixed.prototype.updateCheckboxMixed = function () {
     }
     else {
       this.domNode.setAttribute('aria-checked', 'mixed');
+      this.updateControlledStates();
     }
   }
 };
 
+CheckboxMixed.prototype.updateControlledStates = function () {
+  for (var i = 0; i < this.controlledCheckboxes.length; i++) {
+    this.controlledCheckboxes[i].lastState = this.controlledCheckboxes[i].isChecked();
+  }
+};
+
 CheckboxMixed.prototype.anyLastChecked = function () {
 
   var count = 0;