Unnecessary new (#20138)

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

packages/flutter_tools/test/devfs_test.dart

diff --git a/packages/flutter_tools/test/devfs_test.dart b/packages/flutter_tools/test/devfs_test.dart
index 52ade17..c834d02 100644
--- a/packages/flutter_tools/test/devfs_test.dart
+++ b/packages/flutter_tools/test/devfs_test.dart
@@ -29,14 +29,14 @@
   final AssetBundle assetBundle = AssetBundleFactory.defaultInstance.createBundle();
 
   setUpAll(() {
-    fs = new MemoryFileSystem();
+    fs = MemoryFileSystem();
     filePath = fs.path.join('lib', 'foo.txt');
     filePath2 = fs.path.join('foo', 'bar.txt');
   });
 
   group('DevFSContent', () {
     test('bytes', () {
-      final DevFSByteContent content = new DevFSByteContent(<int>[4, 5, 6]);
+      final DevFSByteContent content = DevFSByteContent(<int>[4, 5, 6]);
       expect(content.bytes, orderedEquals(<int>[4, 5, 6]));
       expect(content.isModified, isTrue);
       expect(content.isModified, isFalse);
@@ -46,7 +46,7 @@
       expect(content.isModified, isFalse);
     });
     test('string', () {
-      final DevFSStringContent content = new DevFSStringContent('some string');
+      final DevFSStringContent content = DevFSStringContent('some string');
       expect(content.string, 'some string');
       expect(content.bytes, orderedEquals(utf8.encode('some string')));
       expect(content.isModified, isTrue);
@@ -65,8 +65,8 @@
   });
 
   group('devfs local', () {
-    final MockDevFSOperations devFSOperations = new MockDevFSOperations();
-    final MockResidentCompiler residentCompiler = new MockResidentCompiler();
+    final MockDevFSOperations devFSOperations = MockDevFSOperations();
+    final MockResidentCompiler residentCompiler = MockResidentCompiler();
 
     setUpAll(() {
       tempDir = _newTempDir(fs);
@@ -84,7 +84,7 @@
       // simulate package
       await _createPackage(fs, 'somepkg', 'somefile.txt');
 
-      devFS = new DevFS.operations(devFSOperations, 'test', tempDir);
+      devFS = DevFS.operations(devFSOperations, 'test', tempDir);
       await devFS.create();
       devFSOperations.expectMessages(<String>['create test']);
       expect(devFS.assetPathsToEvict, isEmpty);
@@ -136,7 +136,7 @@
 
       final File file = fs.file(fs.path.join(basePath, filePath));
       // Set the last modified time to 5 seconds in the past.
-      updateFileModificationTime(file.path, new DateTime.now(), -5);
+      updateFileModificationTime(file.path, DateTime.now(), -5);
       bytes = await devFS.update(
         mainPath: 'lib/foo.txt',
         generator: residentCompiler,
@@ -201,7 +201,7 @@
       const String packageName = 'doubleslashpkg';
       await _createPackage(fs, packageName, 'somefile.txt', doubleSlash: true);
 
-      final Set<String> fileFilter = new Set<String>();
+      final Set<String> fileFilter = Set<String>();
       final List<Uri> pkgUris = <Uri>[fs.path.toUri(basePath)]..addAll(_packages.values);
       for (Uri pkgUri in pkgUris) {
         if (!pkgUri.isAbsolute) {
@@ -229,7 +229,7 @@
     });
 
     testUsingContext('add an asset bundle', () async {
-      assetBundle.entries['a.txt'] = new DevFSStringContent('abc');
+      assetBundle.entries['a.txt'] = DevFSStringContent('abc');
       final int bytes = await devFS.update(
         mainPath: 'lib/foo.txt',
         bundle: assetBundle,
@@ -249,7 +249,7 @@
     });
 
     testUsingContext('add a file to the asset bundle - bundleDirty', () async {
-      assetBundle.entries['b.txt'] = new DevFSStringContent('abcd');
+      assetBundle.entries['b.txt'] = DevFSStringContent('abcd');
       final int bytes = await devFS.update(
         mainPath: 'lib/foo.txt',
         bundle: assetBundle,
@@ -272,7 +272,7 @@
     });
 
     testUsingContext('add a file to the asset bundle', () async {
-      assetBundle.entries['c.txt'] = new DevFSStringContent('12');
+      assetBundle.entries['c.txt'] = DevFSStringContent('12');
       final int bytes = await devFS.update(
         mainPath: 'lib/foo.txt',
         bundle: assetBundle,
@@ -344,12 +344,12 @@
 
   group('devfs remote', () {
     MockVMService vmService;
-    final MockResidentCompiler residentCompiler = new MockResidentCompiler();
+    final MockResidentCompiler residentCompiler = MockResidentCompiler();
 
     setUpAll(() async {
       tempDir = _newTempDir(fs);
       basePath = tempDir.path;
-      vmService = new MockVMService();
+      vmService = MockVMService();
       await vmService.setUp();
     });
     tearDownAll(() async {
@@ -366,7 +366,7 @@
       // simulate package
       await _createPackage(fs, 'somepkg', 'somefile.txt');
 
-      devFS = new DevFS(vmService, 'test', tempDir);
+      devFS = DevFS(vmService, 'test', tempDir);
       await devFS.create();
       vmService.expectMessages(<String>['create test']);
       expect(devFS.assetPathsToEvict, isEmpty);
@@ -403,7 +403,7 @@
       // simulate package
       await _createPackage(fs, 'somepkg', 'somefile.txt');
 
-      devFS = new DevFS(vmService, 'test', tempDir);
+      devFS = DevFS(vmService, 'test', tempDir);
       await devFS.create();
       vmService.expectMessages(<String>['create test']);
       expect(devFS.assetPathsToEvict, isEmpty);
@@ -429,7 +429,7 @@
   MockVM _vm;
 
   MockVMService() {
-    _vm = new MockVM(this);
+    _vm = MockVM(this);
   }
 
   @override
@@ -480,7 +480,7 @@
   Future<Map<String, dynamic>> createDevFS(String fsName) async {
     _service.messages.add('create $fsName');
     if (_devFSExists) {
-      throw new rpc.RpcException(kFileSystemAlreadyExists, 'File system already exists');
+      throw rpc.RpcException(kFileSystemAlreadyExists, 'File system already exists');
     }
     _devFSExists = true;
     return <String, dynamic>{'uri': '$_baseUri'};
@@ -534,7 +534,7 @@
   await pkgFile.parent.create(recursive: true);
   pkgFile.writeAsBytesSync(<int>[11, 12, 13]);
   _packages[pkgName] = fs.path.toUri(pkgFile.parent.path);
-  final StringBuffer sb = new StringBuffer();
+  final StringBuffer sb = StringBuffer();
   _packages.forEach((String pkgName, Uri pkgUri) {
     sb.writeln('$pkgName:$pkgUri');
   });