Add optional startIndex to String.replaceFirst

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.
 
 part of dart.core;
 
 /**
  * A sequence of characters.
  *
  * A string can be either single or multiline. Single line strings are
@@ skipping 391 matching lines @@
    *
    *     string.contains('X', 1);                  // false
    *     string.contains(new RegExp(r'[A-Z]'), 1); // false
    *
    * [startIndex] must not be negative or greater than [length].
    */
   bool contains(Pattern other, [int startIndex = 0]);
 
   /**
    * Returns a new string in which  the first occurence of [from] in this string
-   * is replaced with [to]:
+   * is replaced with [to], starting from [startIndex]:
    *
    *     '0.0001'.replaceFirst(new RegExp(r'0'), ''); // '.0001'
+   *     '0.0001'.replaceFirst(new RegExp(r'0'), '7', 1); // '0.7001'
    */
-  String replaceFirst(Pattern from, String to);
+  String replaceFirst(Pattern from, String to, [int startIndex = 0]);
 
   /**
    * Replaces all substrings that match [from] with [replace].
    *
    * Returns a new string in which the non-overlapping substrings matching
    * [from] (the ones iterated by `from.allMatches(thisString)`) are replaced
    * by the literal string [replace].
    *
    *     'resume'.replaceAll(new RegExp(r'e'), 'é'); // 'résumé'
    *
@@ skipping 308 matching lines @@
         _position = position - 1;
         _currentCodePoint = _combineSurrogatePair(prevCodeUnit, codeUnit);
         return true;
       }
     }
     _position = position;
     _currentCodePoint = codeUnit;
     return true;
   }
 }