Enable strong-mode for pkg/kernel and fix some strong-mode warnings.

pkg/kernel/test/batch_consistency.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 kernel.batch_consistency;
 
 import 'dart:async';
 import 'dart:io';
 import '../bin/dartk.dart' as dartk;
 import '../bin/batch_util.dart';
 import 'package:path/path.dart' as pathlib;
@@ skipping 17 matching lines @@
 
   List<String> options = args.sublist(0, separator);
   List<String> files = args.sublist(separator + 1);
 
   await new Directory(outputDir).create(recursive: true);
 
   testBatchModeConsistency(options, files);
 }
 
 Future<bool> areFilesEqual(String first, String second) async {
-  List<List<int>> bytes = await Future.wait([
-    new File(first).readAsBytes(),
-    new File(second).readAsBytes()
-  ]);
+  List<List<int>> bytes = await Future
+      .wait([new File(first).readAsBytes(), new File(second).readAsBytes()]);
   if (bytes[0].length != bytes[1].length) return false;
   for (int i = 0; i < bytes[0].length; ++i) {
     if (bytes[0][i] != bytes[1][i]) return false;
   }
   return true;
 }
 
 testBatchModeConsistency(List<String> options, List<String> files) {
   var sharedState = new dartk.BatchModeState();
   for (String file in files) {
     test(file, () async {
       var name = pathlib.basename(file);
       List<String> outputFiles = <String>[
         '$outputDir/$name.batch.dill',
         '$outputDir/$name.unbatch.dill'
       ];
       List results = [null, null];
       bool failed = false;
       for (int i = 0; i < 2; ++i) {
-        var args = []..addAll(options)..addAll(['--out', outputFiles[i], file]);
+        var args = <String>[]
+          ..addAll(options)
+          ..addAll(['--out', outputFiles[i], file]);
         var state = (i == 0) ? sharedState : new dartk.BatchModeState();
         try {
           // We run the two executions in a loop to ensure any stack traces
           // are identical in case they both crash at the same place.
           // Crashing at the same place is acceptable for the purpose of
           // this test, there are other tests that check for crashes.
           results[i] = await dartk.batchMain(args, state);
         } catch (e) {
           results[i] = '$e';
           failed = true;
         }
       }
       if (results[0] != results[1]) {
         fail('Batch mode returned ${results[0]}, expected ${results[1]}');
         return;
       }
       if (results[0] == CompilerOutcome.Fail) {
         failed = true;
       }
       if (!failed && !await areFilesEqual(outputFiles[0], outputFiles[1])) {
         fail('Batch mode output differs for $file');
       }
     });
   }
 }