Fix typo in IoSink.flush documentation.

sdk/lib/io/io_sink.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 /**
  * A combined byte and text output.
  *
  * An [IOSink] combines a [StreamSink] of bytes with a [StringSink],
@@ skipping 94 matching lines @@
   /**
    * Adds all elements of the given [stream] to `this`.
    *
    * Returns a [Future] that completes when
    * all elements of the given [stream] are added to `this`.
    */
   Future addStream(Stream<List<int>> stream);
 
   /**
    * Returns a [Future] that completes once all buffered data is accepted by the
-   * to underlying [StreamConsumer].
+   * underlying [StreamConsumer].
    *
    * This method must not be called while an [addStream] is incomplete.
    *
    * NOTE: This is not necessarily the same as the data being flushed by the
    * operating system.
    */
   Future flush();
 
   /**
    * Close the target consumer.
@@ skipping 178 matching lines @@
 
   void writeln([Object object = ""]) {
     write(object);
     write("\n");
   }
 
   void writeCharCode(int charCode) {
     write(new String.fromCharCode(charCode));
   }
 }