introduce ObservableList.listChanges to keep list changes separate from property changes

pkg/polymer_expressions/lib/eval.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.
 
 library polymer_expressions.eval;
 
 import 'dart:async';
 import 'dart:collection';
 
 @MirrorsUsed(metaTargets: const [Reflectable, ObservableProperty],
@@ skipping 571 matching lines @@
 
   _updateSelf(Scope scope) {
     Identifier identifier = left;
     var iterable = right._value;
 
     if (iterable is! Iterable && iterable != null) {
       throw new EvalException("right side of 'in' is not an iterator");
     }
 
     if (iterable is ObservableList) {
-      _subscription = (iterable as ObservableList).changes.listen(
-          (List<ChangeRecord> changes) {
-            if (changes.any((c) => c is ListChangeRecord)) {
-              _invalidate(scope);
-            }
-          });
+      _subscription = iterable.listChanges.listen((_) => _invalidate(scope));
     }
 
     // TODO: make Comprehension observable and update it
     _value = new Comprehension(identifier.value, iterable);
   }
 
   accept(Visitor v) => v.visitInExpression(this);
 }
 
 _toBool(v) => (v == null) ? false : v;
@@ skipping 37 matching lines @@
    * This does not work for calls that need to pass more than one argument.
    */
   call(arg0) => mirror.invoke(symbol, [arg0], null).reflectee;
 }
 
 class EvalException implements Exception {
   final String message;
   EvalException(this.message);
   String toString() => "EvalException: $message";
 }