Strong mode cleaning of many dart2js tests.

tests/compiler/dart2js/dart2js_batch2_test.dart

 // Copyright (c) 2014, 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:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:path/path.dart' as path;
 import 'package:async_helper/async_helper.dart';
@@ skipping 49 matching lines @@
 Future runTests(Process process) {
   String inFile = path.join(tmpDir.path, 'dart2js_batch2_run.dart');
   String outFile = path.join(tmpDir.path, 'out.js');
 
   process.stdin.writeln('--out="$outFile" "$inFile"');
   process.stdin.close();
   Future<String> output = process.stdout.transform(UTF8.decoder).join();
   Future<String> errorOut = process.stderr.transform(UTF8.decoder).join();
   return Future.wait([output, errorOut]).then((result) {
     String stdoutOutput = result[0];
-    String stderrOutput = result[1];
-
     Expect.isFalse(stdoutOutput.contains("crashed"));
   });
 }
 
 void main() {
-  var tmpDir;
   asyncTest(() {
     return setup().then(launchDart2Js).then(runTests).whenComplete(cleanUp);
   });
 }