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

pkg/template_binding/lib/src/binding_delegate.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.
 
-library template_binding.src.binding_delegate;
-
-import 'dart:html';
-import 'package:template_binding/template_binding.dart' show TemplateInstance;
+part of template_binding;
 
 /**
  * Template Bindings native features enables a wide-range of use cases,
  * but (by design) don't attempt to implement a wide array of specialized
  * behaviors.
  *
  * Enabling these features is a matter of implementing and registering a
  * BindingDelegate. A binding delegate is an object which contains one or more
  * delegation functions which implement specialized behavior. This object is
  * registered via [TemplateBindExtension.bindingDelegate]:
@@ skipping 13 matching lines @@
  *     templateBind(query('template'))
  *         ..bindingDelegate = new MySyntax()
  *         ..model = new MyModel();
  *
  *
  * See
  * <http://www.polymer-project.org/platform/template.html#binding-delegate-api>
  * for more information about the binding delegate.
  */
 // TODO(jmesserly): need better api docs here. The link above seems out of date.
-abstract class BindingDelegate {
+class BindingDelegate {
   /**
    * Prepares a binding. This is called immediately after parsing a mustache
    * token with `{{ path }}` in the context of the [node] and the property named
    * [name]. This should return a function that will be passed the actual
    * node and model, and either returns null or an object with a `value`
    * property. This allows the syntax to reinterpret the model for each binding.
    */
   PrepareBindingFunction prepareBinding(String path, String name, Node node)
       => null;
 
   /**
    * Returns a function that can optionally replace the model that will be
    * passed to [TemplateBindExtension.createInstance]. This can be used to
    * implement syntax such as `<template repeat="{{ item in items }}">` by
    * ensuring that the returned model has the "item" name available.
    */
   PrepareInstanceModelFunction prepareInstanceModel(Element template) => null;
 
   /**
    * Returns a function that will be called whenever the position of an item
    * inside this template changes.
    */
   PrepareInstancePositionChangedFunction prepareInstancePositionChanged(
       Element template) => null;
+
+  Expando<_InstanceBindingMap> _bindingMaps;
+
+  // TODO(jmesserly): if we have use this everywhere, we can avoid many
+  // delegate != null checks throughout the code, simplifying things.
+  // For now we just use it for _bindingMaps.
+  static final _DEFAULT = new BindingDelegate();
 }
 
 typedef PrepareBindingFunction(model, Node node, bool oneTime);
 
 typedef PrepareInstanceModelFunction(model);
 
 typedef PrepareInstancePositionChangedFunction(TemplateInstance instance,
     int index);