Fix last-minute-typo.

runtime/lib/string_patch.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.
 
 const int _maxAscii = 0x7f;
 const int _maxLatin1 = 0xff;
 const int _maxUtf16 = 0xffff;
 const int _maxUnicode = 0x10ffff;
 
 patch class String {
@@ skipping 711 matching lines @@
     var slices = [];
     int length = 0;
     if (match.start > 0) {
       length += _addReplaceSlice(slices, 0, match.start);
     }
     slices.add(replacement);
     length += replacement.length;
     if (match.end < this.length) {
       length += _addReplaceSlice(slices, match.end, this.length);
     }
-    bool replacementIsOneByte = _replacement._isOneByte;
+    bool replacementIsOneByte = replacement._isOneByte;
     if (replacementIsOneByte &&
         length < _maxJoinReplaceOneByteStringLength &&
         this._isOneByte) {
-      return _joinReplaceAllOneByteResult(this, matches, length);
+      return _joinReplaceAllOneByteResult(this, slices, length);
     }
     return _joinReplaceAllResult(this, slices, length, replacementIsOneByte);
   }
 
   static String _matchString(Match match) => match[0];
   static String _stringIdentity(String string) => string;
 
   String _splitMapJoinEmptyString(String onMatch(Match match),
                                   String onNonMatch(String nonMatch)) {
     // Pattern is the empty string.
@@ skipping 546 matching lines @@
     for (int g in groups) {
       result.add(group(g));
     }
     return result;
   }
 
   final int start;
   final String input;
   final String pattern;
 }