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

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

Index: tools/dom/templates/html/impl/impl_Element.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Element.darttemplate b/tools/dom/templates/html/impl/impl_Element.darttemplate
index 305d5f2af341c748ea9f57842856cecff93c9be6..821a9f49e2ee7641f61a1a8bd0631e74f5f212c8 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -862,13 +862,15 @@ $endif
   }
 
   /**
-   * Creates an instance of the template.
+   * Creates an instance of the template, using the provided model and binding
+   * delegate.
+   *
    * This is only supported if [isTemplate] is true.
    */
   @Experimental()
-  DocumentFragment createInstance(model, String syntax) {
+  DocumentFragment createInstance(model, BindingDelegate delegate) {
     _ensureTemplate();
-    return TemplateElement.mdvPackage(this).createInstance(model, syntax);
+    return TemplateElement.mdvPackage(this).createInstance(model, delegate);
   }
 
   /**
@@ -884,6 +886,22 @@ $endif
     TemplateElement.mdvPackage(this).model = value;
   }
 
+  /**
+   * The binding delegate which is inherited through the tree. It can be used
+   * to configure custom syntax for `{{bindings}}` inside this template.
+   *
+   * This is only supported if [isTemplate] is true.
+   */
+  @Experimental()
+  BindingDelegate get bindingDelegate =>
+      TemplateElement.mdvPackage(this).bindingDelegate;
+
+  @Experimental()
+  void set bindingDelegate(BindingDelegate value) {
+    _ensureTemplate();
+    TemplateElement.mdvPackage(this).bindingDelegate = value;
+  }
+
   // TODO(jmesserly): const set would be better
   static const _TABLE_TAGS = const {
     'caption': null,