merge to trunk all changes from 36817 until 37378 under the packages: polymer,

pkg/template_binding/lib/src/text.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 template_binding;
 
 /** Extensions to the [Text] API. */
 class _TextExtension extends NodeBindExtension {
   _TextExtension(Text node) : super._(node);
 
   Bindable bind(String name, value, {bool oneTime: false}) {
     // Dart note: 'text' instead of 'textContent' to match the DOM property.
     if (name != 'text') {
       return super.bind(name, value, oneTime: oneTime);
     }
     if (oneTime) {
       _updateText(value);
       return null;
     }
 
-    unbind(name);
     _open(value, _updateText);
-    return bindings[name] = value;
+    return _maybeUpdateBindings(name, value);
   }
 
   _updateText(value) {
     _node.text = _sanitizeValue(value);
   }
 }
 
 /** Called to sanitize the value before it is assigned into the property. */
 _sanitizeValue(value) => value == null ? '' : '$value';