[mdv] template.ref must recursive to find the original source template

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

 // Copyright (c) 2012, 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 $LIBRARYNAME;
 
 class _ChildrenElementList extends ListBase<Element> {
   // Raw Element.
   final Element _element;
   final HtmlCollection _childElements;
@@ skipping 812 matching lines @@
 
 
   /**
    * Gets the template this node refers to.
    * This is only supported if [isTemplate] is true.
    */
   @Experimental()
   Element get ref {
     _ensureTemplate();
 
-    Element ref = null;
+    Element result = null;
     var refId = attributes['ref'];
     if (refId != null) {
       var treeScope = this;
       while (treeScope.parentNode != null) {
         treeScope = treeScope.parentNode;
       }
 
       // Note: JS code tests that getElementById is present. We can't do that
       // easily, so instead check for the types known to implement it.
       if (treeScope is Document ||
           treeScope is ShadowRoot ||
           treeScope is svg.SvgSvgElement) {
 
-        ref = treeScope.getElementById(refId);
+        result = treeScope.getElementById(refId);
       }
     }
 
-    return ref != null ? ref : _templateInstanceRef;
+    if (result == null) {
+      result = _templateInstanceRef;
+      if (result == null) return this;
+    }
+
+    var nextRef = result.ref;
+    return nextRef != null ? nextRef : result;
   }
 
   /**
    * Gets the content of this template.
    * This is only supported if [isTemplate] is true.
    */
   @Experimental()
   DocumentFragment get content {
     _ensureTemplate();
     return _templateContent;
@@ skipping 202 matching lines @@
   const ScrollAlignment._internal(this._value);
   toString() => 'ScrollAlignment.$_value';
 
   /// Attempt to align the element to the top of the scrollable area.
   static const TOP = const ScrollAlignment._internal('TOP');
   /// Attempt to center the element in the scrollable area.
   static const CENTER = const ScrollAlignment._internal('CENTER');
   /// Attempt to align the element to the bottom of the scrollable area.
   static const BOTTOM = const ScrollAlignment._internal('BOTTOM');
 }