Serialize async marker on getters.

pkg/compiler/lib/src/serialization/modelz.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.
 
 /// Implementation of the element model used for deserialiation.
 ///
 /// These classes are created by [ElementDeserializer] triggered by the
 /// [Deserializer].
 
 library dart2js.serialization.modelz;
@@ skipping 1694 matching lines @@
 
   @override
   accept(ElementVisitor visitor, arg) {
     return visitor.visitGetterElement(this, arg);
   }
 
   @override
   bool get isAbstract => _decoder.getBool(Key.IS_ABSTRACT);
 
   @override
-  AsyncMarker get asyncMarker => AsyncMarker.SYNC;
+  AsyncMarker get asyncMarker {
+    return _decoder.getEnum(Key.ASYNC_MARKER, AsyncMarker.values);
+  }
 }
 
 class TopLevelGetterElementZ extends GetterElementZ with LibraryMemberMixin {
   TopLevelGetterElementZ(ObjectDecoder decoder) : super(decoder);
 }
 
 class StaticGetterElementZ extends GetterElementZ
     with ClassMemberMixin, StaticMemberMixin {
   StaticGetterElementZ(ObjectDecoder decoder) : super(decoder);
 }
@@ skipping 589 matching lines @@
   }
 
   @override
   Node get node => throw new UnsupportedError('${this}.node');
 
   @override
   bool get hasNode => false;
 
   String toString() => 'MetadataAnnotationZ(${constant.toDartText()})';
 }