Unnecessary new (#20138)

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests
diff --git a/packages/flutter_goldens/test/flutter_goldens_test.dart b/packages/flutter_goldens/test/flutter_goldens_test.dart
index 0c26bf4..19645ed 100644
--- a/packages/flutter_goldens/test/flutter_goldens_test.dart
+++ b/packages/flutter_goldens/test/flutter_goldens_test.dart
@@ -24,9 +24,9 @@
   MockProcessManager process;
 
   setUp(() {
-    fs = new MemoryFileSystem();
-    platform = new FakePlatform(environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot});
-    process = new MockProcessManager();
+    fs = MemoryFileSystem();
+    platform = FakePlatform(environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot});
+    process = MockProcessManager();
     fs.directory(_kFlutterRoot).createSync(recursive: true);
     fs.directory(_kRepositoryRoot).createSync(recursive: true);
     fs.file(_kVersionFile).createSync(recursive: true);
@@ -37,7 +37,7 @@
     GoldensClient goldens;
 
     setUp(() {
-      goldens = new GoldensClient(
+      goldens = GoldensClient(
         fs: fs,
         platform: platform,
         process: process,
@@ -47,7 +47,7 @@
     group('prepare', () {
       test('performs minimal work if versions match', () async {
         when(process.run(any, workingDirectory: anyNamed('workingDirectory')))
-            .thenAnswer((_) => new Future<io.ProcessResult>.value(io.ProcessResult(123, 0, _kGoldensVersion, '')));
+            .thenAnswer((_) => Future<io.ProcessResult>.value(io.ProcessResult(123, 0, _kGoldensVersion, '')));
         await goldens.prepare();
 
         // Verify that we only spawned `git rev-parse HEAD`
@@ -65,17 +65,17 @@
     FlutterGoldenFileComparator comparator;
 
     setUp(() {
-      fs = new MemoryFileSystem();
+      fs = MemoryFileSystem();
       final Directory flutterRoot = fs.directory('/path/to/flutter')..createSync(recursive: true);
       final Directory goldensRoot = flutterRoot.childDirectory('bin/cache/goldens')..createSync(recursive: true);
       final Directory testDirectory = goldensRoot.childDirectory('test/foo/bar')..createSync(recursive: true);
-      comparator = new FlutterGoldenFileComparator(testDirectory.uri, fs: fs);
+      comparator = FlutterGoldenFileComparator(testDirectory.uri, fs: fs);
     });
 
     group('fromDefaultComparator', () {
       test('calculates the basedir correctly', () async {
-        final MockGoldensClient goldens = new MockGoldensClient();
-        final MockLocalFileComparator defaultComparator = new MockLocalFileComparator();
+        final MockGoldensClient goldens = MockGoldensClient();
+        final MockLocalFileComparator defaultComparator = MockLocalFileComparator();
         final Directory flutterRoot = fs.directory('/foo')..createSync(recursive: true);
         final Directory goldensRoot = flutterRoot.childDirectory('bar')..createSync(recursive: true);
         when(goldens.fs).thenReturn(fs);
@@ -91,7 +91,7 @@
     group('compare', () {
       test('throws if golden file is not found', () async {
         try {
-          await comparator.compare(new Uint8List.fromList(<int>[1, 2, 3]), Uri.parse('test.png'));
+          await comparator.compare(Uint8List.fromList(<int>[1, 2, 3]), Uri.parse('test.png'));
           fail('TestFailure expected but not thrown');
         } on TestFailure catch (error) {
           expect(error.message, contains('Could not be compared against non-existent file'));
@@ -102,7 +102,7 @@
         final File goldenFile = fs.file('/path/to/flutter/bin/cache/goldens/test/foo/bar/test.png')
           ..createSync(recursive: true);
         goldenFile.writeAsBytesSync(<int>[4, 5, 6], flush: true);
-        final bool result = await comparator.compare(new Uint8List.fromList(<int>[1, 2, 3]), Uri.parse('test.png'));
+        final bool result = await comparator.compare(Uint8List.fromList(<int>[1, 2, 3]), Uri.parse('test.png'));
         expect(result, isFalse);
       });
 
@@ -110,7 +110,7 @@
         final File goldenFile = fs.file('/path/to/flutter/bin/cache/goldens/test/foo/bar/test.png')
           ..createSync(recursive: true);
         goldenFile.writeAsBytesSync(<int>[1, 2, 3], flush: true);
-        final bool result = await comparator.compare(new Uint8List.fromList(<int>[1, 2, 3]), Uri.parse('test.png'));
+        final bool result = await comparator.compare(Uint8List.fromList(<int>[1, 2, 3]), Uri.parse('test.png'));
         expect(result, isTrue);
       });
     });
@@ -119,7 +119,7 @@
       test('creates golden file if it does not already exist', () async {
         final File goldenFile = fs.file('/path/to/flutter/bin/cache/goldens/test/foo/bar/test.png');
         expect(goldenFile.existsSync(), isFalse);
-        await comparator.update(Uri.parse('test.png'), new Uint8List.fromList(<int>[1, 2, 3]));
+        await comparator.update(Uri.parse('test.png'), Uint8List.fromList(<int>[1, 2, 3]));
         expect(goldenFile.existsSync(), isTrue);
         expect(goldenFile.readAsBytesSync(), <int>[1, 2, 3]);
       });
@@ -128,7 +128,7 @@
         final File goldenFile = fs.file('/path/to/flutter/bin/cache/goldens/test/foo/bar/test.png')
           ..createSync(recursive: true);
         goldenFile.writeAsBytesSync(<int>[4, 5, 6], flush: true);
-        await comparator.update(Uri.parse('test.png'), new Uint8List.fromList(<int>[1, 2, 3]));
+        await comparator.update(Uri.parse('test.png'), Uint8List.fromList(<int>[1, 2, 3]));
         expect(goldenFile.readAsBytesSync(), <int>[1, 2, 3]);
       });
     });