All strong mode cleaning of dart2js.

tests/compiler/dart2js/serialization/test_helper.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_test_helper;
 
-import 'dart:collection';
-import 'package:compiler/src/common/resolution.dart';
-import 'package:compiler/src/constants/expressions.dart';
-import 'package:compiler/src/constants/values.dart';
-import 'package:compiler/src/compiler.dart';
-import 'package:compiler/src/elements/elements.dart';
-import 'package:compiler/src/elements/entities.dart';
-import 'package:compiler/src/elements/resolution_types.dart';
-import 'package:compiler/src/elements/types.dart';
-import 'package:compiler/src/kernel/elements.dart';
-import 'package:compiler/src/kernel/element_map_impl.dart';
-import 'package:compiler/src/serialization/equivalence.dart';
-import 'package:compiler/src/util/util.dart';
-import 'package:expect/expect.dart';
 import 'test_data.dart';
 
 /// Returns the test arguments for testing the [index]th skipped test. The
 /// [skip] count is used to check that [index] is a valid index.
 List<String> testSkipped(int index, int skip) {
   if (index < 0 || index >= skip) {
     throw new ArgumentError('Invalid skip index $index');
   }
   return ['${index}', '${index + 1}'];
 }
@@ skipping 11 matching lines @@
   }
 
   if (index == 1 && skip != 0) {
     return ['${skip}', segmentNumber(index)];
   } else if (index == count) {
     return [segmentNumber(index - 1)];
   } else {
     return [segmentNumber(index - 1), segmentNumber(index)];
   }
 }