Remove usage of dart:utf from dart:io.

sdk/lib/io/io.dart

Index: sdk/lib/io/io.dart
diff --git a/sdk/lib/io/io.dart b/sdk/lib/io/io.dart
index 37a65c1226bf95e5473f084a2f3d0f5b055b0565..e390d319ce4f99733f0f545b0380bd85ae94cdaa 100644
--- a/sdk/lib/io/io.dart
+++ b/sdk/lib/io/io.dart
@@ -4,7 +4,7 @@
 
 /**
  * File, socket, HTTP, and other I/O support for server applications.
- * 
+ *
  * The IO library is used for Dart server applications,
  * which run on a stand-alone Dart VM from the command line.
  * *This library does not work in browser based applications.*
@@ -23,7 +23,6 @@ import 'dart:convert';
 import 'dart:isolate';
 import 'dart:json' as JSON;
 import 'dart:math';
-import 'dart:utf';
 import 'dart:typed_data';
 
 part 'bytes_builder.dart';