update to polymer js 0.5.1

pkg/observe/lib/src/path_observer.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 observe.src.path_observer;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:math' show min;
 
@@ skipping 215 matching lines @@
       obj = _getObjectProperty(obj, _segments[i]);
     }
     return _setObjectProperty(obj, _segments[end], value);
   }
 
   void _iterateObjects(Object obj, void observe(obj, prop)) {
     if (!isValid || isEmpty) return;
 
     int i = 0, last = _segments.length - 1;
     while (obj != null) {
-      // _segments[0] is passed to indicate that we are only observing that
-      // property of obj. See observe declaration in _ObserveSet.
-      observe(obj, _segments[0]);
+      // _segments[i] is passed to indicate that we are only observing that
+      // property of obj. See observe declaration in _ObservedSet.
+      observe(obj, _segments[i]);
 
       if (i >= last) break;
       obj = _getObjectProperty(obj, _segments[i++]);
     }
   }
 
   // Dart note: it doesn't make sense to have compiledGetValueFromFn in Dart.
 }
 
 
@@ skipping 609 matching lines @@
 
   void close(_Observer obs) {
     if (_observers.isNotEmpty) return;
 
     if (_objects != null) {
       for (var sub in _objects) sub.cancel();
       _objects = null;
     }
     _rootObject = null;
     _rootObjectProperties = null;
+    if (identical(_lastSet, this)) _lastSet = null;
   }
 
   /// Observe now takes a second argument to indicate which property of an
   /// object is being observed, so we don't trigger change notifications on
   /// changes to unrelated properties.
   void observe(Object obj, Object prop) {
     if (identical(obj, _rootObject)) _rootObjectProperties.add(prop);
     if (obj is ObservableList) _observeStream(obj.listChanges);
     if (obj is Observable) _observeStream(obj.changes);
   }
@@ skipping 41 matching lines @@
       if (observer._isOpen) observer._iterateObjects(observe);
     }
 
     for (var observer in _observers.toList(growable: false)) {
       if (observer._isOpen) observer._check();
     }
   }
 }
 
 const int _MAX_DIRTY_CHECK_CYCLES = 1000;