fix logic for detecting when in an auto-binding element

pkg/polymer/lib/src/build/linter.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.
 
 /// Logic to validate that developers are correctly using Polymer constructs.
 /// This is mainly used to produce warnings for feedback in the editor.
 library polymer.src.build.linter;
 
 import 'dart:async';
 import 'dart:convert';
@@ skipping 177 matching lines @@
   }
 
   void visitElement(Element node) {
     switch (node.localName) {
       case 'link': _validateLinkElement(node); break;
       case 'element': _validateElementElement(node); break;
       case 'polymer-element': _validatePolymerElement(node); break;
       case 'script': _validateScriptElement(node); break;
       case 'template':
         var isTag = node.attributes['is'];
+        var oldInAutoBindingElement = _inAutoBindingElement;
         if (isTag != null && AUTO_BINDING_ELEMENTS.contains(isTag)) {
           _inAutoBindingElement = true;
         }
         _validateNormalElement(node);
         super.visitElement(node);
-        _inAutoBindingElement = false;
+        _inAutoBindingElement = oldInAutoBindingElement;
         break;
       default:
         _validateNormalElement(node);
         super.visitElement(node);
         break;
     }
   }
 
   void run(Document doc) {
     visit(doc);
@@ skipping 246 matching lines @@
     upDirCount = segments.length - 2;
   }
   var reachOutPrefix = '../' * upDirCount;
   return USE_POLYMER_HTML.create({'reachOutPrefix': reachOutPrefix});
 }
 
 const List<String> INTERNALLY_DEFINED_ELEMENTS = 
     const ['auto-binding-dart', 'polymer-element'];
 const List<String> AUTO_BINDING_ELEMENTS =
     const ['auto-binding-dart', 'auto-binding'];