fix travis bots

lib/src/compiler/command.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:analyzer/src/generated/source.dart' show Source;
 import 'package:analyzer/src/summary/package_bundle_reader.dart'
     show InSummarySource;
 import 'package:args/args.dart' show ArgParser, ArgResults;
 import 'package:args/command_runner.dart' show UsageException;
 import 'package:path/path.dart' as path;
 
 import '../analyzer/context.dart' show AnalyzerOptions;
-import 'compiler.dart'
-    show BuildUnit, CompilerOptions, JSModuleFile, ModuleCompiler;
+import 'compiler.dart' show BuildUnit, CompilerOptions, ModuleCompiler;
 import 'module_builder.dart';
 
 final ArgParser _argParser = () {
   var argParser = new ArgParser()
     ..addFlag('help', abbr: 'h', help: 'Display this message.')
     ..addOption('out',
         abbr: 'o', allowMultiple: true, help: 'Output file (required).')
     ..addOption('module-root',
         help: 'Root module directory.\n'
             'Generated module paths are relative to this root.')
@@ skipping 148 matching lines @@
     '\n\n${_argParser.usage}';
 
 void _usageException(String message) {
   throw new UsageException(message, _usageMessage);
 }
 
 /// Thrown when the input source code has errors.
 class CompileErrorException implements Exception {
   toString() => '\nPlease fix all errors before compiling (warnings are okay).';
 }