Fix build for pub after new analyzer_experimental snapshot.

pkg/observe/lib/transform.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.
 
 /**
  * Code transform for @observable. The core transformation is relatively
  * straightforward, and essentially like an editor refactoring.
  */
 library observe.transform;
 
@@ skipping 155 matching lines @@
     declaresObservable = true;
   }
 
   // Track fields that were transformed.
   var instanceFields = new Set<String>();
   var getters = new List<String>();
   var setters = new List<String>();
 
   for (var member in cls.members) {
     if (member is FieldDeclaration) {
-      bool isStatic = _hasKeyword(member.keyword, Keyword.STATIC);
-      if (isStatic) {
+      if (member.isStatic) {
         if (_hasObservable(member)){
           logger.warning('Static fields can no longer be observable. '
               'Observable fields should be put in an observable objects.',
               _getSpan(file, member));
         }
         continue;
       }
       if (_hasObservable(member)) {
         if (!declaresObservable) {
           logger.warning('Observable fields should be put in an observable'
@@ skipping 132 matching lines @@
 $type __\$$name$initializer;
 $type get $name => __\$$name;
 set $name($type value) {
   __\$$name = notifyPropertyChange(const Symbol('$name'), __\$$name, value);
 }
 '''.replaceAll('\n', '\n$indent'));
   }
 
   code.edit(begin, end, '$replace');
 }