http_date: produce leading zero on day component

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 28 matching lines @@
    */
   static String format(DateTime date) {
     const List wkday = const ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
     const List month = const ["Jan", "Feb", "Mar", "Apr", "May", "Jun",
                               "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];
 
     DateTime d = date.toUtc();
     StringBuffer sb = new StringBuffer()
         ..write(wkday[d.weekday - 1])
         ..write(", ")
+        ..write(d.day <= 9 ? "0" : "")
         ..write(d.day.toString())
         ..write(" ")
         ..write(month[d.month - 1])
         ..write(" ")
         ..write(d.year.toString())
         ..write(d.hour <= 9 ? " 0" : " ")
         ..write(d.hour.toString())
         ..write(d.minute <= 9 ? ":0" : ":")
         ..write(d.minute.toString())
         ..write(d.second <= 9 ? ":0" : ":")
@@ skipping 246 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);
   }
 }