pkg/compiler: fix imports

pkg/compiler/bin/resolver.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.
 
 import 'dart:io';
 
 import 'package:args/args.dart';
 import 'package:compiler/src/apiimpl.dart';
-import 'package:compiler/src/dart2js.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/null_compiler_output.dart';
-import 'package:compiler/src/source_file_provider.dart';
 import 'package:compiler/src/options.dart';
 import 'package:compiler/src/serialization/json_serializer.dart';
+import 'package:compiler/src/source_file_provider.dart';
 import 'package:package_config/discovery.dart';
 
 main(var argv) async {
   var parser = new ArgParser();
   parser.addOption('deps', abbr: 'd', allowMultiple: true);
   parser.addOption('out', abbr: 'o');
   parser.addOption('library-root', abbr: 'l');
   var args = parser.parse(argv);
 
   var resolutionInputs = args['deps']
@@ skipping 37 matching lines @@
       inputs.map((lib) => compiler.libraryLoader.lookupLibrary(lib)).toList();
 
   var serializer =
       compiler.serialization.createSerializer(librariesToSerialize);
   var text = serializer.toText(const JsonSerializationEncoder());
 
   var outFile = args['out'] ?? 'out.data';
 
   await new File(outFile).writeAsString(text);
 }