Add optimized _OneByteString.toLowerCase.

sdk/lib/io/http_date.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.io;
 
 /**
  * Utility functions for working with dates with HTTP specific date
  * formats.
  */
@@ skipping 243 matching lines @@
       int index = 0;
       for (; index < s.length && isDigit(s[index]); index++);
       return int.parse(s.substring(0, index));
     }
 
     var tokens = [];
     while (!isEnd()) {
       while (!isEnd() && isDelimiter(date[position])) position++;
       int start = position;
       while (!isEnd() && isNonDelimiter(date[position])) position++;
-      tokens.add(date.substring(start, position).toLowerCase());
+      tokens.add(_ASCII.toLowerCase(date.substring(start, position)));
       while (!isEnd() && isDelimiter(date[position])) position++;
     }
 
     String timeStr;
     String dayOfMonthStr;
     String monthStr;
     String yearStr;
 
     for (var token in tokens) {
       if (token.length < 1) continue;
@@ skipping 30 matching lines @@
     int hour = toInt(timeList[0]);
     int minute = toInt(timeList[1]);
     int second = toInt(timeList[2]);
     if (hour > 23) error();
     if (minute > 59) error();
     if (second > 59) error();
 
     return new DateTime.utc(year, month, dayOfMonth, hour, minute, second, 0);
   }
 }