Allow function as replacement argument to String.replaceAll.

sdk/lib/core/string.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.
 
 /**
  * The String class represents character strings. Strings are
  * immutable. A string is represented by a list of 32-bit Unicode
  * scalar character codes accessible through the [charCodeAt] or the
  * [charCodes] method.
  */
@@ skipping 81 matching lines @@
   bool contains(Pattern other, [int startIndex]);
 
   /**
    * Returns a new string where the first occurence of [from] in this string
    * is replaced with [to].
    */
   String replaceFirst(Pattern from, String to);
 
   /**
    * Returns a new string where all occurences of [from] in this string
-   * are replaced with [to].
+   * are replaced with a [String] depending on [replace].
+   *
+   * If [replace] is a [Function], it's called with the [Match] generated
+   * by the pattern, and its result is used as replacement.
+   * Otherwise, [replace] must be a [String], which is directly used as
+   * the replacement.
    */
-  String replaceAll(Pattern from, String to);
+  String replaceAll(Pattern from, var replace);
 
   /**
    * Splits the string around matches of [pattern]. Returns
    * a list of substrings.
    */
   List<String> split(Pattern pattern);
 
   /**
    * Returns a list of the characters of this string.
    */
@@ skipping 28 matching lines @@
    * Joins all the given strings to create a new string.
    */
   external static String join(List<String> strings, String separator);
 
   /**
    * Concatenates all the given strings to create a new string.
    */
   external static String concatAll(List<String> strings);
 
 }