Reorganize equivalence test helpers

tests/compiler/dart2js/serialization/library_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_library_test;
 
 import 'dart:async';
 import 'dart:io';
-import '../memory_compiler.dart';
 import 'package:async_helper/async_helper.dart';
-import 'package:compiler/src/common.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common/names.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/diagnostics/invariant.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/serialization/json_serializer.dart';
 import 'package:compiler/src/serialization/serialization.dart';
 import 'package:expect/expect.dart';
-
+import '../equivalence/check_functions.dart';
+import '../memory_compiler.dart';
 import 'equivalence_test.dart';
-import 'test_helper.dart';
-import 'resolved_ast_test.dart';
 import 'helper.dart';
 
 main(List<String> arguments) {
   // Ensure that we can print out constant expressions.
   DEBUG_MODE = true;
 
   Uri entryPoint;
   String outPath;
   int shardCount = 3;
   bool prettyPrint = false;
@@ skipping 95 matching lines @@
         compiler2.libraryLoader.lookupLibrary(library1.canonicalUri);
     if (library2 == null) {
       throw new ArgumentError('No library ${library1.canonicalUri} found.');
     }
     checkLibraryContent('library1', 'library2', 'library', library1, library2);
     checkAllResolvedAsts(compiler1, compiler2);
     checkAllImpacts(compiler1, compiler2);
   }
   Expect.isFalse(compiler2.reporter.hasReportedError, "Unexpected errors");
 }