Custom Syntax's are now enabled via template.bindingDelegate =

tools/dom/templates/html/impl/impl_HTMLTemplateElement.darttemplate

 // 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.
 
 // WARNING: Do not edit - generated code.
 
 part of $LIBRARYNAME;
 
-
 /**
  * Model-Driven Views (MDV)'s 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 in MDV is a matter of implementing and registering an
  * MDV Custom Syntax. A Custom Syntax is an object which contains one or more
  * delegation functions which implement specialized behavior. This object is
- * registered with MDV via [TemplateElement.syntax]:
+ * registered with MDV via [Element.bindingDelegate]:
  *
  *
  * HTML:
- *     <template bind syntax="MySyntax">
+ *     <template bind>
  *       {{ What!Ever('crazy')->thing^^^I+Want(data) }}
  *     </template>
  *
  * Dart:
- *     class MySyntax extends CustomBindingSyntax {
+ *     class MySyntax extends BindingDelegate {
  *       getBinding(model, path, name, node) {
  *         // The magic happens here!
  *       }
  *     }
- *
  *     ...
- *
- *     TemplateElement.syntax['MySyntax'] = new MySyntax();
+ *     query('template').bindingDelegate = new MySyntax();
+ *     query('template').model = new MyModel();
  *
  * See <https://github.com/polymer-project/mdv/blob/master/docs/syntax.md> for
  * more information about Custom Syntax.
  */
-// TODO(jmesserly): if this is just one method, a function type would make it
-// more Dart-friendly.
+// TODO(jmesserly): move this type to the MDV package? Two issues: we'd lose
+// type annotation on [Element.bindingDelegate], and "mdv" is normally imported
+// with a prefix.
 @Experimental()
-abstract class CustomBindingSyntax {
+abstract class BindingDelegate {
   /**
    * This syntax method allows for a custom interpretation of the contents of
    * mustaches (`{{` ... `}}`).
    *
    * When a template is inserting an instance, it will invoke this method for
    * each mustache which is encountered. The function is invoked with four
    * arguments:
    *
    * - [model]: The data context for which this instance is being created.
    * - [path]: The text contents (trimmed of outer whitespace) of the mustache.
@@ skipping 28 matching lines @@
    *   instance.
    * - [model]: The data context for which this instance is being created.
    *
    * The template element will always use the return value of `getInstanceModel`
    * as the model for the new instance. If the syntax does not wish to override
    * the value, it should simply return the `model` value it was passed.
    */
   getInstanceModel(Element template, model) => model;
 }
 
-
 @Experimental()
 $(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 $!MEMBERS
 
   // For real TemplateElement use the actual DOM .content field instead of
   // our polyfilled expando.
   @Experimental()
   DocumentFragment get content => $dom_content;
 
 
@@ skipping 181 matching lines @@
 tr[template],
 td[template],
 caption[template],
 colgroup[template],
 col[template],
 option[template] {
   display: none;
 }''';
     document.head.append(style);
   }
-
-  /**
-   * A mapping of names to Custom Syntax objects. See [CustomBindingSyntax] for
-   * more information.
-   */
-  @Experimental()
-  static Map<String, CustomBindingSyntax> syntax = {};
 }