fixes #130, accept anything with `iterator` in for loops

lib/src/utils.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.
 
 /// Holds a couple utility functions used at various places in the system.
 library dev_compiler.src.utils;
 
 import 'dart:io';
 
 import 'package:path/path.dart' as path;
@@ skipping 406 matching lines @@
     });
     // Add getters.
     element.accessors
         .where((member) => !member.isStatic && member.isGetter)
         .forEach((member) {
       map[member.name] = member.type.returnType;
     });
   }
   return map;
 }
+
+/// Searches all supertype, in order of most derived members, to see if any
+/// [match] a condition. If so, returns the first match, otherwise returns null.
+InterfaceType findSupertype(InterfaceType type, bool match(InterfaceType t)) {
+  for (var m in type.mixins.reversed) {
+    if (match(m)) return m;
+  }
+  var s = type.superclass;
+  if (s == null) return null;
+
+  if (match(s)) return type;
+  return findSupertype(s, match);
+}