Fix warnings and hints.

pkg/utf/lib/utf.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.
 
 /**
- * Support for encoding and decoding Unicode characters in UTF-8, UTF-16, and 
+ * Support for encoding and decoding Unicode characters in UTF-8, UTF-16, and
  * UTF-32.
  */
 library utf;
+
 import "dart:async";
 import "dart:collection";
+
 part "utf_stream.dart";
 part "utf8.dart";
 part "utf16.dart";
 part "utf32.dart";
 
 // TODO(jmesserly): would be nice to have this on String (dartbug.com/6501).
 /**
  * Provide a list of Unicode codepoints for a given string.
  */
 List<int> stringToCodepoints(String str) {
@@ skipping 238 matching lines @@
     _offset -= by;
   }
 
   int get remaining => _end - _offset - 1;
 
   void skip([int count = 1]) {
     _offset += count;
   }
 }