Fix type warnings in dart:io library.

runtime/bin/file.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.
 
 
 /**
  * FileMode describes the modes in which a file can be opened.
  */
 class FileMode {
   static final READ = const FileMode(0);
@@ skipping 114 matching lines @@
    * Synchronously get the canonical full path corresponding to the file name.
    */
   String fullPathSync();
 
   /**
    * Create a new independent input stream for the file. The file
    * input stream must be closed when no longer used to free up system
    * resources.  The [inputStreamHandler] is called with the result
    * when the openInputStream operation completes.
    */
-  InputStream openInputStream();
+  void openInputStream();
 
   /**
    * Synchronously create a new independent input stream for the
    * file. The file input stream must be closed when no longer used to
    * free up system resources.
    *
    * Even though this call to open the input stream is synchronous the
    * input stream itself is asynchronous as is the case for all input
    * streams.
    */
   InputStream openInputStreamSync();
 
   /**
    * Creates a new independent output stream for the file. The file
    * output stream must be closed when no longer used to free up
-   * system resources.
+   * system resources.  The [outputStreamHandler] is called with the result
+   * when the openOutputStream operation completes.
    *
    * An output stream can be opened in two modes:
    *
    * FileMode.WRITE: create the stream and truncate the underlying
    * file to length zero.
    *
    * FileMode.APPEND: create the stream and set the position to the end of
    * the underlying file.
    *
    * By default the mode is FileMode.WRITE.
    */
-  OutputStream openOutputStream([FileMode mode]);
+  void openOutputStream([FileMode mode]);
 
   /**
    * Synchronously creates a new independent output stream for the
    * file. The file output stream must be closed when no longer used
    * to free up system resources.
    *
    * See [openOutputStream] for information on the [:mode:] argument.
    *
    * Even though this call to open the output stream is synchronous
    * the output stream itself is asynchronous as is the case for all
@@ skipping 330 matching lines @@
    */
   void set errorHandler(void handler(String error));
 }
 
 
 class FileIOException implements Exception {
   const FileIOException([String this.message = ""]);
   String toString() => "FileIOException: $message";
   final String message;
 }