fix(ngOptionsDirective): use equals function if attr.multiple(to save performance issues)

Author: m-amr

src/ng/directive/ngOptions.js

@@ -733,7 +733,8 @@ var ngOptionsDirective = ['$compile', '$parse', function($compile, $parse) {
         // Check to see if the value has changed due to the update to the options
         if (!ngModelCtrl.$isEmpty(previousValue)) {
           var nextValue = selectCtrl.readValue();
-          if (!equals(previousValue, nextValue)) {
+          var isNotPrimitive = ngOptions.trackBy || multiple;
+          if (isNotPrimitive ? !equals(previousValue, nextValue) : previousValue !== nextValue) {
             ngModelCtrl.$setViewValue(nextValue);
             ngModelCtrl.$render();
           }