Remove FileSystem.lastModified

pkg/front_end/test/physical_file_system_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.
 // SharedOptions=--supermixin
 
 library front_end.test.physical_file_system_test;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io' as io;
@@ skipping 78 matching lines @@
 
   test_exists_fileExists() async {
     new io.File(path).writeAsStringSync('contents');
     expect(await file.exists(), isTrue);
   }
 
   test_hashCode_samePath() {
     expect(file.hashCode, entityForPath(p.join(tempPath, 'file.txt')).hashCode);
   }
 
-  test_lastModified_doesNotExist() {
-    expect(file.lastModified(), _throwsFileSystemException);
-  }
-
-  test_lastModified_increasesOnEachChange() async {
-    new io.File(path).writeAsStringSync('contents1');
-    var mod1 = await file.lastModified();
-
-    // Pause to ensure the file-system time-stamps are different.
-    await new Future.delayed(new Duration(seconds: 1));
-    new io.File(path).writeAsStringSync('contents2');
-    var mod2 = await file.lastModified();
-    expect(mod2.isAfter(mod1), isTrue);
-
-    await new Future.delayed(new Duration(seconds: 1));
-    var path2 = p.join(tempPath, 'file2.txt');
-    new io.File(path2).writeAsStringSync('contents2');
-    var file2 = entityForPath(path2);
-    var mod3 = await file2.lastModified();
-    expect(mod3.isAfter(mod2), isTrue);
-  }
-
   test_readAsBytes_badUtf8() async {
     // A file containing invalid UTF-8 can still be read as raw bytes.
     List<int> bytes = [0xc0, 0x40]; // Invalid UTF-8
     new io.File(path).writeAsBytesSync(bytes);
     expect(await file.readAsBytes(), bytes);
   }
 
   test_readAsBytes_doesNotExist() {
     expect(file.readAsBytes(), _throwsFileSystemException);
   }
@@ skipping 132 matching lines @@
       tempDirectory.deleteSync(recursive: true);
     } on io.FileSystemException {
       // Sometimes on Windows the delete fails with errno 32
       // (ERROR_SHARING_VIOLATION: The process cannot access the file because it
       // is being used by another process).  Wait 1 second and try again.
       await new Future.delayed(new Duration(seconds: 1));
       tempDirectory.deleteSync(recursive: true);
     }
   }
 }