Move WorldImpact to universe/world_impact.dart

tests/compiler/dart2js/serialization_analysis_test.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 dart2js.serialization_analysis_test;
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/compiler.dart';
-import 'package:compiler/src/enqueue.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/serialization/serialization.dart';
 import 'package:compiler/src/serialization/json_serializer.dart';
 import 'package:compiler/src/serialization/task.dart';
+import 'package:compiler/src/universe/world_impact.dart';
 import 'memory_compiler.dart';
 
 const List<Test> TESTS = const <Test>[
   const Test(const {
     'main.dart': 'main() => print("Hello World");'
   }),
 
   const Test(const {
     'main.dart': 'main() => print("Hello World", 0);'
   },
@@ skipping 205 matching lines @@
   @override
   WorldImpact computeWorldImpact(Element element) {
     return const WorldImpact();
   }
 
   @override
   bool isDeserialized(Element element) {
     return deserializedLibraries.contains(element.library);
   }
 }