Add line handler to string stream

runtime/bin/input_stream.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.
 
 /**
  * Input is read from a given input stream. Such an input stream can
  * be an endpoint, e.g., a socket or a file, or another input stream.
  * Multiple input streams can be chained together to operate collaboratively
  * on a given input.
  */
@@ skipping 53 matching lines @@
 
   /**
    * Reads as many characters as is available from the stream. If no data is
    * available null will be returned.
    */
   String read();
 
   /**
    * Reads the next line from the stream. The line ending characters
    * will not be part og the returned string. If a full line is not
-   * available null will be returned.
+   * available null will be returned. The line break character(s) are
+   * discarded.
    */
   String readLine();
 
   /**
    * Returns whether the stream has been closed. There might still be
    * more data to read.
    */
   bool get closed();
 
   /**
    * Returns the encoding used to decode the binary data into characters.
    */
   String get encoding();
 
   /**
-   * Sets the handler that gets called when data is available.
+   * Sets the handler that gets called when data is available. The two
+   * handlers [dataHandler} and [lineHandler] are mutually exclusive
+   * and setting one will remove the other.
    */
   void set dataHandler(void callback());
 
   /**
+   * Sets the handler that gets called when a line is available. The
+   * two handlers [dataHandler} and [lineHandler] are mutually
+   * exclusive and setting one will remove the other.
+   */
+  void set lineHandler(void callback());
+
+  /**
    * Sets the handler that gets called when there will be no more data
    * available in the stream.
    */
   void set closeHandler(void callback());
 
   /**
    * Sets the handler that gets called when the underlying
    * communication channel gets into some kind of error situation.
    */
   void set errorHandler(void callback());
 }
 
 
 class StreamException implements Exception {
   const StreamException([String this.message = ""]);
   String toString() => "StreamException: $message";
   final String message;
 }