Enable most of the constant AST serialization for AST-based summaries.

pkg/analyzer/lib/src/summary/summarize_elements.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.
 
 library serialization.elements;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/type.dart';
@@ skipping 47 matching lines @@
  */
 class _ConstExprSerializer extends AbstractConstExprSerializer {
   final _LibrarySerializer serializer;
 
   _ConstExprSerializer(this.serializer);
 
   UnlinkedTypeRefBuilder serializeIdentifier(Identifier identifier) {
     Element element = identifier.staticElement;
     assert(element != null);
     // TODO(scheglov) how to serialize element references?
-    operations.add(UnlinkedConstOperation.pushReference);
     return new UnlinkedTypeRefBuilder(
         reference: serializer._getElementReferenceId(element));
   }
 
   @override
   UnlinkedTypeRefBuilder serializeType(TypeName typeName) {
     DartType type = typeName != null ? typeName.type : DynamicTypeImpl.instance;
     return serializer.serializeTypeRef(type, null);
   }
 }
@@ skipping 758 matching lines @@
     } else if (element is ClassElement) {
       kind = ReferenceKind.classOrEnum;
     } else if (element is FunctionElement) {
       kind = ReferenceKind.topLevelFunction;
     } else {
       throw new Exception('Unexpected element kind: ${element.runtimeType}');
     }
     return kind;
   }
 }