Implement File.lastModified.

tests/standalone/io/file_fuzz_test.dart

 // Copyright (c) 2012, 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.
 
 // 'fuzz' test the file APIs by providing unexpected type arguments. The test
 // passes if the VM does not crash.
 
 #import('dart:io');
 #import('dart:isolate');
 
 #import('fuzz_support.dart');
 
 fuzzSyncMethods() {
   typeMapping.forEach((k, v) {
     doItSync(() {
       var f = new File(v);
       doItSync(f.existsSync);
       doItSync(f.createSync);
       doItSync(f.deleteSync);
       doItSync(f.directorySync);
       doItSync(f.lengthSync);
+      doItSync(f.modifiedSync);
       doItSync(f.fullPathSync);
       doItSync(() => f.openInputStream().onError = (e) => null);
       doItSync(f.readAsBytesSync);
       doItSync(f.readAsTextSync);
       doItSync(f.readAsLinesSync);
       typeMapping.forEach((k2, v2) {
         doItSync(() => f.openSync(v2));
         doItSync(() => f.openOutputStream(v2).onError = (e) => null);
         doItSync(() => f.readAsTextSync(v2));
         doItSync(() => f.readAsLinesSync(v2));
       });
     });
   });
 }
 
 fuzzAsyncMethods() {
   var port = new ReceivePort();
   var futures = [];
   typeMapping.forEach((k, v) {
     doItSync(() {
       var f = new File(v);
       futures.add(doItAsync(f.exists));
       futures.add(doItAsync(f.delete));
       futures.add(doItAsync(f.directory));
       futures.add(doItAsync(f.length));
+      futures.add(doItAsync(f.modified));
       futures.add(doItAsync(f.open));
       futures.add(doItAsync(f.fullPath));
       futures.add(doItAsync(f.readAsBytes));
       futures.add(doItAsync(f.readAsLines));
       futures.add(doItAsync(f.readAsText));
       typeMapping.forEach((k2, v2) {
         futures.add(doItAsync(() => f.open(v2)));
         futures.add(doItAsync(() => f.readAsText(v2)));
         futures.add(doItAsync(() => f.readAsLines(v2)));
       });
@@ skipping 59 matching lines @@
     temp.deleteRecursivelySync();
   });
 }
 
 main() {
   fuzzSyncMethods();
   fuzzAsyncMethods();
   fuzzSyncRandomAccessMethods();
   fuzzAsyncRandomAccessMethods();
 }