dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/dart2js.dart

 // Copyright (c) 2013, 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.cmdline;
 
-import 'dart:async' show Future, EventSink;
+import 'dart:async' show Future;
 import 'dart:convert' show UTF8, LineSplitter;
-import 'dart:io'
-    show
-        exit,
-        File,
-        FileMode,
-        Platform,
-        RandomAccessFile,
-        FileSystemException,
-        stdin,
-        stderr;
+import 'dart:io' show exit, File, FileMode, Platform, stdin, stderr;
+
+import 'package:package_config/discovery.dart' show findPackages;
 
 import '../compiler.dart' as api;
 import 'commandline_options.dart';
+import 'filenames.dart';
 import 'io/source_file.dart';
 import 'source_file_provider.dart';
-import 'filenames.dart';
+import 'util/command_line.dart';
 import 'util/uri_extras.dart';
 import 'util/util.dart' show stackTraceFilePrefix;
-import 'util/command_line.dart';
-import 'package:package_config/discovery.dart' show findPackages;
 
 const String LIBRARY_ROOT = '../../../../../sdk';
 const String OUTPUT_LANGUAGE_DART = 'Dart';
 
 /**
  * A string to identify the revision or build.
  *
  * This ID is displayed if the compiler crashes and in verbose mode, and is
  * an aid in reproducing bug reports.
  *
@@ skipping 743 matching lines @@
       } else if (exitCode == 253) {
         print(">>> TEST CRASH");
       } else {
         print(">>> TEST FAIL");
       }
       stderr.writeln(">>> EOF STDERR");
       subscription.resume();
     });
   });
 }