Add dummy dart:html library for documentation.

lib/html/doc/interface/FileWriter.dartdoc

+// 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.
+
+// WARNING:
+//   This file contains documentation that is merged into the real source.
+//   Do not make code changes here.
+
+/// @domName FileWriter
+interface FileWriter extends EventTarget {
+
+  /**
+   * @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent
+   */
+  FileWriterEvents get on();
+
+  static final int DONE = 2;
+
+  static final int INIT = 0;
+
+  static final int WRITING = 1;
+
+  /** @domName FileWriter.error */
+  final FileError error;
+
+  /** @domName FileWriter.length */
+  final int length;
+
+  /** @domName FileWriter.position */
+  final int position;
+
+  /** @domName FileWriter.readyState */
+  final int readyState;
+
+  /** @domName FileWriter.abort */
+  void abort();
+
+  /** @domName FileWriter.addEventListener */
+  void $dom_addEventListener(String type, EventListener listener, [bool useCapture]);
+
+  /** @domName FileWriter.dispatchEvent */
+  bool $dom_dispatchEvent(Event evt);
+
+  /** @domName FileWriter.removeEventListener */
+  void $dom_removeEventListener(String type, EventListener listener, [bool useCapture]);
+
+  /** @domName FileWriter.seek */
+  void seek(int position);
+
+  /** @domName FileWriter.truncate */
+  void truncate(int size);
+
+  /** @domName FileWriter.write */
+  void write(Blob data);
+}
+
+interface FileWriterEvents extends Events {
+
+  EventListenerList get abort();
+
+  EventListenerList get error();
+
+  EventListenerList get progress();
+
+  EventListenerList get write();
+
+  EventListenerList get writeEnd();
+
+  EventListenerList get writeStart();
+}