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

pkg/mdv/lib/mdv.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.
 
 // TODO(jmesserly): more commentary here.
 /**
  * This library provides access to Model-Driven-Views APIs on HTML elements.
  * More information can be found at: <https://github.com/toolkitchen/mdv>.
  */
 library mdv;
@@ skipping 47 matching lines @@
  * Binds all mustaches recursively starting from the [root] node.
  *
  * Note: this is not an official Model-Driven-Views API; it is intended to
  * support binding the [ShadowRoot]'s content to a model.
  */
 // TODO(jmesserly): this is needed to avoid two <template> nodes when using
 // bindings in a custom element's template. See also:
 // https://github.com/polymer-project/polymer/blob/master/src/bindMDV.js#L68
 // Called from:
 // https://github.com/polymer-project/polymer/blob/master/src/register.js#L99
-void bindModel(Node root, model, [CustomBindingSyntax syntax]) {
-  _addBindings(root, model, syntax);
+void bindModel(Node root, model, [BindingDelegate delegate]) {
+  _addBindings(root, model, delegate);
 }
 
 
 // TODO(jmesserly): investigate if expandos give us enough performance.
 
 // The expando for storing our MDV wrappers.
 //
 // In general, we need state associated with the nodes. Rather than having a
 // bunch of individual expandos, we keep one per node.
 //
@@ skipping 23 matching lines @@
   } else if (node is Node) {
     wrapper = new _NodeExtension(node);
   } else {
     // TODO(jmesserly): this happens for things like CompoundBinding.
     wrapper = node;
   }
 
   _mdvExpando[node] = wrapper;
   return wrapper;
 }