fix(chips): item name in autcomplete

Defer to a function as the item name expression is nested in contact chips.

fixes #4109

closes #4111

Author: Ty Potter

src/components/chips/js/contactChipsController.js

@@ -24,6 +24,11 @@ MdContactChipsCtrl.prototype.queryContact = function(searchText) {
 };
 
 
+MdContactChipsCtrl.prototype.itemName = function(item) {
+  return item[this.contactName];
+};
+
+
 MdContactChipsCtrl.prototype.filterSelectedContacts = function(contact) {
   return this.contacts.indexOf(contact) == -1;
 };

src/components/chips/js/contactChipsDirective.js

@@ -58,7 +58,7 @@
               md-selected-item="$mdContactChipsCtrl.selectedItem"\
               md-search-text="$mdContactChipsCtrl.searchText"\
               md-items="item in $mdContactChipsCtrl.queryContact($mdContactChipsCtrl.searchText)"\
-              md-item-text="$mdContactChipsCtrl.mdContactName"\
+              md-item-text="$mdContactChipsCtrl.itemName(item)"\
               md-no-cache="true"\
               md-autoselect\
               placeholder="{{$mdContactChipsCtrl.contacts.length == 0 ?\