Refactor unittests

tests/compiler/dart2js/serialization/compilation_test.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_compilation_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/common/backend_api.dart';
 import 'package:compiler/src/common/names.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/filenames.dart';
-import 'memory_compiler.dart';
-import 'serialization_helper.dart';
-import 'serialization_test_data.dart';
-import 'output_collector.dart';
+import '../memory_compiler.dart';
+import 'helper.dart';
+import 'test_data.dart';
+import '../output_collector.dart';
 
 main(List<String> args) {
   asyncTest(() async {
     Arguments arguments = new Arguments.from(args);
     String serializedData = await serializeDartCore(
         arguments: arguments,
         serializeResolvedAst: true);
     if (arguments.filename != null) {
       Uri entryPoint = Uri.base.resolve(nativeToUriPath(arguments.filename));
       await compile(serializedData, entryPoint, null);
@@ skipping 26 matching lines @@
                 Flags.noSourceMaps],
       outputProvider: outputCollector,
       beforeRun: (Compiler compiler) {
         deserialize(compiler, serializedData, deserializeResolvedAst: true);
       });
   if (verbose) {
     print(outputCollector.getOutput('', 'js'));
   }
 }