make sure we follow the whole super chain

lib/transformer.dart

 // Copyright (c) 2015, 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.
 library initialize.transformer;
 
 import 'dart:async';
 import 'dart:collection' show Queue;
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:barback/barback.dart';
@@ skipping 197 matching lines @@
       if (seen.contains(library)) continue;
       _readLibraries(library, seen);
     }
 
     // Read annotations in this order: library, top level methods, classes.
     _readAnnotations(library);
     for (var method in _topLevelMethodsOfLibrary(library, seen)) {
       _readAnnotations(method);
     }
     for (var clazz in _classesOfLibrary(library, seen)) {
-      var superClass = clazz.supertype;
-      while (superClass != null) {
+      readSuperClassAnnotations(InterfaceType superClass) {
+        if (superClass == null) return;
+        readSuperClassAnnotations(superClass.superclass);
         if (_readAnnotations(superClass.element) &&
             superClass.element.library != clazz.library) {
           _logger.warning(
               'We have detected a cycle in your import graph when running '
               'initializers on ${clazz.name}. This means the super class '
               '${superClass.name} has a dependency on this library '
               '(possibly transitive).');
         }
-        superClass = superClass.superclass;
       }
+      readSuperClassAnnotations(clazz.supertype);
       _readAnnotations(clazz);
     }
   }
 
   bool _readAnnotations(Element element) {
     var found = false;
     if (element.metadata.isEmpty) return found;
 
     var metaNodes;
     var node = element.node;
@@ skipping 214 matching lines @@
     error = false;
   } else {
     error = true;
   }
   if (error) {
     print('Bad value for "$field" in the initialize transformer. '
         'Expected either one String or a list of Strings.');
   }
   return files;
 }