Migrate from touch cmd to dart's built-in API (#8313)

This enables us to run more tests on Windows.

packages/flutter_tools/lib/src/base/file_system.dart

@@ -77,7 +77,7 @@ void copyDirectorySync(Directory srcDir, Directory destDir) {
     destDir.createSync(recursive: true);
 
   srcDir.listSync().forEach((FileSystemEntity entity) {
-    String newPath = fs.path.join(destDir.path, fs.path.basename(entity.path));
+    String newPath = destDir.fileSystem.path.join(destDir.path, entity.basename);
     if (entity is File) {
       File newFile = destDir.fileSystem.file(newPath);
       newFile.writeAsBytesSync(entity.readAsBytesSync());

packages/flutter_tools/test/dependency_checker_test.dart

@@ -19,7 +19,7 @@ void main()  {
   group('DependencyChecker', () {
     final String basePath = fs.path.dirname(fs.path.fromUri(platform.script));
     final String dataPath = fs.path.join(basePath, 'data', 'dart_dependencies_test');
-    MemoryFileSystem testFileSystem;
+    FileSystem testFileSystem;
 
     setUp(() {
       Cache.disableLocking();
@@ -56,7 +56,8 @@ void main()  {
       // Set 'package:self/bar.dart' file modification time to be in the future.
       updateFileModificationTime(barPath, baseTime, 10);
       expect(dependencyChecker.check(baseTime), isTrue);
-    });
+    }, skip: io.Platform.isWindows); // TODO(goderbauer): enable when sky_snapshot is ready on Windows
+
     testUsingContext('syntax error', () {
       final String testPath = fs.path.join(dataPath, 'syntax_error');
       final String mainPath = fs.path.join(testPath, 'main.dart');
@@ -85,11 +86,11 @@ void main()  {
     /// Tests that the flutter tool doesn't crash and displays a warning when its own location
     /// changed since it was last referenced to in a package's .packages file.
     testUsingContext('moved flutter sdk', () async {
-      String destinationPath = '/some/test/location';
+      Directory destinationPath = fs.systemTempDirectory.createTempSync('dependency_checker_test_');
       // Copy the golden input and let the test run in an isolated temporary in-memory file system.
-      copyDirectorySync(
-        const LocalFileSystem().directory(fs.path.join(dataPath, 'changed_sdk_location')),
-        fs.directory(destinationPath));
+      LocalFileSystem localFileSystem = const LocalFileSystem();
+      Directory sourcePath =  localFileSystem.directory(localFileSystem.path.join(dataPath, 'changed_sdk_location'));
+      copyDirectorySync(sourcePath, destinationPath);
       fs.currentDirectory = destinationPath;
 
       // Doesn't matter what commands we run. Arbitrarily list devices here.
@@ -98,5 +99,5 @@ void main()  {
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
     });
-  }, skip: io.Platform.isWindows); // TODO(goderbauer): Migrate test away from 'touch' bash command.
+  });
 }

packages/flutter_tools/test/devfs_test.dart

@@ -4,7 +4,6 @@
 
 import 'dart:async';
 import 'dart:convert';
-import 'dart:io' as io;
 
 import 'package:flutter_tools/src/asset.dart';
 import 'package:flutter_tools/src/base/io.dart';
@@ -115,7 +114,7 @@ void main() {
       ]);
       expect(devFS.assetPathsToEvict, isEmpty);
       expect(bytes, 6);
-    }, skip: io.Platform.isWindows); // TODO(goderbauer): enable when updateFileModificationTime is ported to Windows
+    });
     testUsingContext('delete a file from the local file system', () async {
       File file = fs.file(fs.path.join(basePath, filePath));
       await file.delete();

packages/flutter_tools/test/src/common.dart

@@ -3,11 +3,10 @@
 // found in the LICENSE file.
 
 import 'package:args/command_runner.dart';
-import 'package:process/process.dart';
 import 'package:test/test.dart';
 
 import 'package:flutter_tools/src/base/common.dart';
-import 'package:flutter_tools/src/base/context.dart';
+import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/runner/flutter_command.dart';
 import 'package:flutter_tools/src/runner/flutter_command_runner.dart';
 
@@ -23,15 +22,7 @@ void updateFileModificationTime(String path,
                                 DateTime baseTime,
                                 int seconds) {
   DateTime modificationTime = baseTime.add(new Duration(seconds: seconds));
-  String argument =
-      '${modificationTime.year}'
-      '${modificationTime.month.toString().padLeft(2, "0")}'
-      '${modificationTime.day.toString().padLeft(2, "0")}'
-      '${modificationTime.hour.toString().padLeft(2, "0")}'
-      '${modificationTime.minute.toString().padLeft(2, "0")}'
-      '.${modificationTime.second.toString().padLeft(2, "0")}';
-  ProcessManager processManager = context[ProcessManager];
-  processManager.runSync(<String>['touch', '-t', argument, path]);
+  fs.file(path).setLastModifiedSync(modificationTime);
 }
 
 /// Matcher for functions that throw ToolExit.