fix auto-binding-dart example

pkg/polymer/lib/auto_binding.dart

Index: pkg/polymer/lib/auto_binding.dart
diff --git a/pkg/polymer/lib/auto_binding.dart b/pkg/polymer/lib/auto_binding.dart
index 1e1d0b69c14029d6939e92613a52c8c8c9dadfd5..ab12bca7833420859a4a8c4486e6244670872b8c 100644
--- a/pkg/polymer/lib/auto_binding.dart
+++ b/pkg/polymer/lib/auto_binding.dart
@@ -20,7 +20,7 @@ import 'package:template_binding/template_binding.dart';
  *
  * Example:
  *
- *     <template is="auto-binding-dart">
+ *     <template id="my-template" is="auto-binding-dart">
  *       <div>Say something: <input value="{{value}}"></div>
  *       <div>You said: {{value}}</div>
  *       <button on-tap="{{buttonTap}}">Tap me!</button>
@@ -30,7 +30,7 @@ import 'package:template_binding/template_binding.dart';
  *       import 'package:polymer/polymer.dart';
  *
  *       main() {
- *         var template = document.querySelector('template');
+ *         var template = document.querySelector('#my-template');

[Siggi Cherem (dart-lang), 2014/09/11 15:44:22]

might be worth mentioning in the example that using an id is useful because of
how the project compilation works (what you mentioned in that bug).

  *         template.model = new MyModel();
  *       }
  *