Enable strong mode in DDC, fix all warnings/errors

test/worker/worker_test.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:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:bazel_worker/bazel_worker.dart';
 // TODO(jakemac): Remove once this is a part of the testing library.
@@ skipping 23 matching lines @@
       inputDartFile.writeAsStringSync('main() => print("hello world");');
     });
 
     tearDown(() {
       if (inputDartFile.existsSync()) inputDartFile.deleteSync();
       if (outputJsFile.existsSync()) outputJsFile.deleteSync();
       if (argsFile.existsSync()) argsFile.deleteSync();
     });
 
     test('can compile in worker mode', () async {
-      var args = new List.from(executableArgs)..add('--persistent_worker');
+      var args = executableArgs.toList()..add('--persistent_worker');
       var process = await Process.start('dart', args);
       var messageGrouper = new AsyncMessageGrouper(process.stdout);
 
       var request = new WorkRequest();
       request.arguments.addAll(compilerArgs);
       process.stdin.add(protoToDelimitedBuffer(request));
 
       var response = await _readResponse(messageGrouper);
       expect(response.exitCode, EXIT_CODE_OK, reason: response.output);
       expect(response.output, isEmpty);
@@ skipping 11 matching lines @@
       expect(outputJsFile.readAsStringSync(), contains('goodbye world'));
 
       process.kill();
 
       // TODO(jakemac): This shouldn't be necessary, but it is for the process
       // to exit properly.
       expect(await messageGrouper.next, isNull);
     });
 
     test('can compile in basic mode', () {
-      var args = new List.from(executableArgs)..addAll(compilerArgs);
+      var args = executableArgs.toList()..addAll(compilerArgs);
       var result = Process.runSync('dart', args);
 
       expect(result.exitCode, EXIT_CODE_OK);
       expect(result.stdout, isEmpty);
       expect(result.stderr, isEmpty);
       expect(outputJsFile.existsSync(), isTrue);
     });
 
     test('can compile in basic mode with args in a file', () async {
       argsFile.createSync();
       argsFile.writeAsStringSync(compilerArgs.join('\n'));
-      var args = new List.from(executableArgs)..add('@${argsFile.path}');
+      var args = executableArgs.toList()..add('@${argsFile.path}');
       var process = await Process.start('dart', args);
       stderr.addStream(process.stderr);
       var futureProcessOutput = process.stdout.map(UTF8.decode).toList();
 
       expect(await process.exitCode, EXIT_CODE_OK);
       expect((await futureProcessOutput).join(), isEmpty);
       expect(outputJsFile.existsSync(), isTrue);
     });
   });
 
@@ skipping 154 matching lines @@
           startsWith('[warning] ${unusedPartWarningCode.message} '
               '(test/worker/greeting.dart, line 1, col 1)'));
       expect(result.stderr, isEmpty);
       expect(result.exitCode, 0);
       expect(outJS.existsSync(), isTrue);
     });
   });
 }
 
 Future<WorkResponse> _readResponse(MessageGrouper messageGrouper) async {
-  var buffer = await messageGrouper.next;
+  var buffer = (await messageGrouper.next) as List<int>;
   try {
     return new WorkResponse.fromBuffer(buffer);
   } catch (_) {
     var bufferAsString =
         buffer == null ? '' : 'String: ${UTF8.decode(buffer)}\n';
     throw 'Failed to parse response:\nbytes: $buffer\n$bufferAsString';
   }
 }