Add readAsStringSync() to File.

pkg/analyzer/test/file_system/memory_file_system_test.dart

 // Copyright (c) 2014, 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.
 
 library test.memory_file_system;
 
 import 'dart:async';
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
@@ skipping 103 matching lines @@
   }
 
   void test_parent() {
     provider.newFile('/foo/bar/file.txt', 'content');
     File file = provider.getResource('/foo/bar/file.txt');
     Resource parent = file.parent;
     expect(parent, new isInstanceOf<Folder>());
     expect(parent.path, equals('/foo/bar'));
   }
 
+  void test_readAsStringSync_doesNotExist() {
+    File file = provider.getResource('/test.txt');
+    expect(() {
+      file.readAsStringSync();
+    }, throwsA(_isFileSystemException));
+  }
+
+  void test_readAsStringSync_exists() {
+    File file = provider.newFile('/file.txt', 'abc');
+    expect(file.readAsStringSync(), 'abc');
+  }
+
   void test_shortName() {
     File file = provider.getResource('/foo/bar/file.txt');
     expect(file.shortName, 'file.txt');
   }
 
   void test_toString() {
     File file = provider.getResource('/foo/bar/file.txt');
     expect(file.toString(), '/foo/bar/file.txt');
   }
 }
@@ skipping 406 matching lines @@
     return new Future.delayed(Duration.ZERO, computation);
   }
 
   _watchingFolder(String path, test(List<WatchEvent> changesReceived)) {
     Folder folder = provider.getResource(path);
     var changesReceived = <WatchEvent>[];
     folder.changes.listen(changesReceived.add);
     return test(changesReceived);
   }
 }