Revert "Switch libraries to using new tags."

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 character strings. Strings are
  * immutable. A string is represented by a list of 32-bit Unicode
  * scalar character codes accessible through the [charCodeAt] or the
  * [charCodes] method.
  */
 abstract class String implements Comparable, Pattern, Sequence<String> {
   /**
    * Allocates a new String for the specified [charCodes].
    */
@@ skipping 110 matching lines @@
    * where all characters  are made lower case. Returns [:this:] otherwise.
    */
   String toLowerCase();
 
   /**
    * If this string is not already all uper case, returns a new string
    * where all characters are made upper case. Returns [:this:] otherwise.
    */
   String toUpperCase();
 }