Remove use of deprecated mirror API from pkg/observe.

pkg/observe/lib/src/observable.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.observable;
 
 import 'dart:async';
 import 'dart:collection';
 
 // Note: ObservableProperty is in this list only for the unusual use case of
@@ skipping 64 matching lines @@
     // Register this object for dirty checking purposes.
     registerObservable(this);
 
     var mirror = reflect(this);
     var values = new Map<Symbol, Object>();
 
     // Note: we scan for @observable regardless of whether the base type
     // actually includes this mixin. While perhaps too inclusive, it lets us
     // avoid complex logic that walks "with" and "implements" clauses.
     for (var type = mirror.type; type != objectType; type = type.superclass) {
-      for (var field in type.variables.values) {
-        if (field.isFinal || field.isStatic || field.isPrivate) continue;
+      for (var field in type.declarations.values) {
+        if (field is! VariableMirror ||
+            field.isFinal ||
+            field.isStatic ||
+            field.isPrivate) continue;
 
         for (var meta in field.metadata) {
           if (meta.reflectee is ObservableProperty) {
             var name = field.simpleName;
             // Note: since this is a field, getting the value shouldn't execute
             // user code, so we don't need to worry about errors.
             values[name] = mirror.getField(name).reflectee;
             break;
           }
         }
@@ skipping 98 matching lines @@
     Object newValue) {
 
   if (obj.hasObservers && oldValue != newValue) {
     obj.notifyChange(new PropertyChangeRecord(obj, field, oldValue, newValue));
   }
   return newValue;
 }
 
 // NOTE: this is not exported publically.
 final objectType = reflectClass(Object);