Remove frog from the repository.

frog/file_system_memory.dart

-// Copyright (c) 2011, 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('file_system_memory');
-
-#import('file_system.dart');
-
-/**
- * [FileSystem] implementation a memory buffer.
- */
-class MemoryFileSystem implements FileSystem {
-  StringBuffer buffer;
-
-  MemoryFileSystem() : this.buffer = new StringBuffer();
-
-  void writeString(String outfile, String text) {
-    buffer.add(text);
-  }
-
-  String readAll(String filename) {
-    return buffer.toString();
-  }
-
-  bool fileExists(String filename) {
-    return true;
-  }
-}