Allow <template if="{{ expr }}"> to be equivalent to template bind

pkg/mdv/lib/src/template_iterator.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of mdv;
 
 // This code is a port of Model-Driven-Views:
 // https://github.com/polymer-project/mdv
 // The code mostly comes from src/template_element.js
 
@@ skipping 183 matching lines @@
 
   static Object resolveInputs(Map values) {
     if (values.containsKey('if') && !_toBoolean(values['if'])) {
       return null;
     }
 
     if (values.containsKey('repeat')) {
       return values['repeat'];
     }
 
-    if (values.containsKey('bind')) {
+    if (values.containsKey('bind') || values.containsKey('if')) {
       return [values['bind']];
     }
 
     return null;
   }
 
   void valueChanged(value) {
     // TODO(jmesserly): should PathObserver do this for us?
     var oldValue = _lastValue;
     _lastValue = value;
@@ skipping 147 matching lines @@
         nodeExt._templateIterator = null;
       }
     }
 
     _nodeOrCustom(node).unbindAll();
     for (var c = node.firstChild; c != null; c = c.nextNode) {
       _unbindAllRecursively(c);
     }
   }
 }