Rename String.concat to operator+.

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;
 
 /**
  * The String class represents sequences of characters. Strings are
  * immutable. A string is represented by a sequence of Unicode UTF-16
  * code units accessible through the [codeUnitAt] or the
@@ skipping 117 matching lines @@
   bool get isEmpty;
 
   /**
    * Creates a new string by concatenating this string with [other].
    *
    * A sequence of strings can be concatenated by using [Iterable.join]:
    *
    *     var strings = ['foo', 'bar', 'geez'];
    *     var concatenated = strings.join();
    */
+  String operator +(String other);
+
+  /**
+   * *Deprecated* Use [operator+] instead.
+   */
+  @deprecated
   String concat(String other);
 
   /**
    * Returns a slice of this string from [startIndex] to [endIndex].
    *
    * If [startIndex] is omitted, it defaults to the start of the string.
    *
    * If [endIndex] is omitted, it defaults to the end of the string.
    *
    * If either index is negative, it's taken as a negative index from the
@@ skipping 302 matching lines @@
         _position = position - 1;
         _currentCodePoint = _combineSurrogatePair(prevCodeUnit, codeUnit);
         return true;
       }
     }
     _position = position;
     _currentCodePoint = codeUnit;
     return true;
   }
 }