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

sdk/lib/html/dart2js/html_dart2js.dart

 /// The Dart HTML library.
 ///
 /// For examples, see
 /// [Dart HTML5 Samples](https://github.com/dart-lang/dart-html5-samples)
 /// on Github.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol, deprecated;
@@ skipping 8564 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 20852 matching lines @@
       _position = nextPosition;
       return true;
     }
     _current = null;
     _position = _array.length;
     return false;
   }
 
   T get current => _current;
 }