Rename String.concat to operator+.

pkg/intl/lib/src/date_format_field.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 intl;
 
 /**
  * This is a private class internal to DateFormat which is used for formatting
  * particular fields in a template. e.g. if the format is hh:mm:ss then the
  * fields would be "hh", ":", "mm", ":", and "ss". Each type of field knows
@@ skipping 241 matching lines @@
 
   String format24Hours(DateTime date) {
     return padTo(width, date.hour);
   }
 
   String formatFractionalSeconds(DateTime date) {
     // Always print at least 3 digits. If the width is greater, append 0s
     var basic = padTo(3, date.millisecond);
     if (width - 3 > 0) {
       var extra = padTo(width - 3, 0);
-      return basic.concat(extra);
+      return basic + extra;
     } else {
       return basic;
     }
   }
 
   String formatAmPm(DateTime date) {
     var hours = date.hour;
     var index = (date.hour >= 12) && (date.hour < 24) ? 1 : 0;
     var ampm = symbols.AMPMS;
     return ampm[index];
@@ skipping 124 matching lines @@
     var basicString = toBePrinted.toString();
     if (basicString.length >= width) return basicString;
     var buffer = new StringBuffer();
     for (var i = 0; i < width - basicString.length; i++) {
       buffer.write('0');
      }
     buffer.write(basicString);
     return buffer.toString();
   }
 }