Enable strong mode in DDC, fix all warnings/errors

test/codegen_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.
 
 /// Tests code generation.
 ///
 /// Runs Dart Dev Compiler on all input in the `codegen` directory and checks
 /// that the output is what we expected.
 library dev_compiler.test.codegen_test;
 
@@ skipping 45 matching lines @@
 // TODO(jmesserly): switch this to a .packages file.
 final packageUrlMappings = {
   'package:expect/expect.dart': path.join(codegenDir, 'expect.dart'),
   'package:async_helper/async_helper.dart':
       path.join(codegenDir, 'async_helper.dart'),
   'package:js/js.dart': path.join(codegenDir, 'packages', 'js', 'js.dart')
 };
 
 final codeCoverage = Platform.environment.containsKey('COVERALLS_TOKEN');
 
-main(arguments) {
+main(List<String> arguments) {
   if (arguments == null) arguments = [];
   ArgResults args = argParser.parse(arguments);
   var filePattern = new RegExp(args.rest.length > 0 ? args.rest[0] : '.');
 
   var sdkDir = path.join(repoDirectory, 'gen', 'patched_sdk');
   var sdkSummaryFile =
       path.join(testDirectory, '..', 'lib', 'runtime', 'dart_sdk.sum');
   var analyzerOptions = new AnalyzerOptions(
       customUrlMappings: packageUrlMappings,
       dartSdkSummaryPath: sdkSummaryFile);
@@ skipping 191 matching lines @@
 
 String _moduleForLibrary(Source source) {
   var scheme = source.uri.scheme;
   if (scheme == 'package') {
     return source.uri.pathSegments.first;
   }
   throw new Exception('Module not found for library "${source.fullName}"');
 }
 
 List<String> _setUpTests(List<String> testDirs, RegExp filePattern) {
-  var testFiles = [];
+  var testFiles = <String>[];
 
   for (var testDir in testDirs) {
     for (var file in _listFiles(path.join(codegenDir, testDir), filePattern,
         recursive: true)) {
       var relativePath = path.relative(file, from: codegenDir);
       var outputPath = path.join(codegenTestDir, relativePath);
 
       _ensureDirectory(path.dirname(outputPath));
 
       // Copy it over. We do this even for multitests because import_self_test
@@ skipping 94 matching lines @@
 /// Simplified from ParseDartTask.resolveDirective.
 String _resolveDirective(UriBasedDirective directive) {
   StringLiteral uriLiteral = directive.uri;
   String uriContent = uriLiteral.stringValue;
   if (uriContent != null) {
     uriContent = uriContent.trim();
     directive.uriContent = uriContent;
   }
   return directive.validate() == null ? uriContent : null;
 }