Introduce LibraryEntity

pkg/compiler/lib/src/serialization/serialization_util.dart

 // Copyright (c) 2016, 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 dart2js.serialization.util;
 
 import '../common.dart';
 import '../constants/expressions.dart';
 import '../elements/resolution_types.dart';
 import '../diagnostics/messages.dart';
 import '../elements/elements.dart';
 import '../elements/modelx.dart' show WrappedMessage;
 import '../resolution/access_semantics.dart';
 import '../resolution/operators.dart';
 import '../resolution/send_structure.dart';
 import '../universe/call_structure.dart';
 import '../universe/selector.dart';
 import 'keys.dart';
 import 'serialization.dart';
 
 /// Serialize [name] into [encoder].
 void serializeName(Name name, ObjectEncoder encoder) {
   encoder.setString(Key.NAME, name.text);
   encoder.setBool(Key.IS_SETTER, name.isSetter);
   if (name.library != null) {
-    encoder.setElement(Key.LIBRARY, name.library);
+    LibraryElement library = name.library;
+    encoder.setElement(Key.LIBRARY, library);
   }
 }
 
 /// Deserialize a [Name] from [decoder].
 Name deserializeName(ObjectDecoder decoder) {
   String name = decoder.getString(Key.NAME);
   bool isSetter = decoder.getBool(Key.IS_SETTER);
   LibraryElement library = decoder.getElement(Key.LIBRARY, isOptional: true);
   return new Name(name, library, isSetter: isSetter);
 }
@@ skipping 544 matching lines @@
   ObjectDecoder sourceSpanDecoder =
       object.getObject(Key.SOURCE_SPAN, isOptional: true);
   if (sourceSpanDecoder != null) {
     sourceSpan = deserializeSourceSpan(sourceSpanDecoder);
   }
   MessageKind messageKind = object.getEnum(Key.KIND, MessageKind.values);
   Map<String, dynamic> messageArguments =
       deserializeMessageArguments(object, Key.ARGUMENTS);
   return new WrappedMessage(sourceSpan, messageKind, messageArguments);
 }