Switch libraries to using new tags.

sdk/lib/utf/utf8.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.utf;
+
 const int _UTF8_ONE_BYTE_MAX = 0x7f;
 const int _UTF8_TWO_BYTE_MAX = 0x7ff;
 const int _UTF8_THREE_BYTE_MAX = 0xffff;
 
 const int _UTF8_LO_SIX_BIT_MASK = 0x3f;
 
 const int _UTF8_FIRST_BYTE_OF_TWO_BASE = 0xc0;
 const int _UTF8_FIRST_BYTE_OF_THREE_BASE = 0xe0;
 const int _UTF8_FIRST_BYTE_OF_FOUR_BASE = 0xf0;
 const int _UTF8_FIRST_BYTE_OF_FIVE_BASE = 0xf8;
@@ skipping 236 matching lines @@
     if (validSequence && nonOverlong && inRange) {
       return value;
     } else if (replacementCodepoint != null) {
       return replacementCodepoint;
     } else {
       throw new ArgumentError(
           "Invalid UTF8 at ${utf8EncodedBytesIterator.position - j}");
     }
   }
 }