Remove unused import in polymer, fix comment.

pkg/polymer/lib/src/instance.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 polymer;
 
 /// Use this annotation to publish a field as an attribute. For example:
 ///
 ///     class MyPlaybackElement extends PolymerElement {
 ///       // This will be available as an HTML attribute, for example:
@@ skipping 608 matching lines @@
     return true;
   }
 
   void unregisterObservers() {
     if (_observers == null) return;
     for (var sub in _observers.values) sub.cancel();
     _observers.clear();
     _observers = null;
   }
 
-  /// Bind a [property] in this object to a [path] in model. *Note* in Dart it
+  /// Bind the [name] property in this element to [bindable]. *Note* in Dart it
   /// is necessary to also define the field:
   ///
   ///     var myProperty;
   ///
   ///     ready() {
   ///       super.ready();
-  ///       bindProperty(#myProperty, this, 'myModel.path.to.otherProp');
+  ///       bindProperty(#myProperty,
+  ///           new PathObserver(this, 'myModel.path.to.otherProp'));
   ///     }
   Bindable bindProperty(Symbol name, Bindable bindable) {
     // Dart note: normally we only reach this code when we know it's a
     // property, but if someone uses bindProperty directly they might get a
     // NoSuchMethodError either from the getField below, or from the setField
     // inside PolymerBinding. That doesn't seem unreasonable, but it's a slight
     // difference from Polymer.js behavior.
 
     if (_bindLog.isLoggable(Level.FINE)) {
       _bindLog.fine('bindProperty: [$bindable] to [${localName}].[name]');
@@ skipping 373 matching lines @@
     if (_sub != null) {
       if (_eventsLog.isLoggable(Level.FINE)) {
         _eventsLog.fine(
             'event.remove: [$_node].$_eventName => [$_model].$_path())');
       }
      _sub.cancel();
       _sub = null;
     }
   }
 }