Some more removals of dart:utf.

tools/ddbg.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.
 
 // Simple interactive debugger shell that connects to the Dart VM's debugger
 // connection port.
 
 import "dart:convert";
 import "dart:io";
 import "dart:json" as json;
-import "dart:utf";
 import "dart:async";
 
 
 Map<int, Completer> outstandingCommands;
 
 Socket vmSock;
 String vmData;
 var stdinSubscription;
 var vmSubscription;
 int seqNum = 0;
@@ skipping 612 matching lines @@
       process.stdin.close();
       process.exitCode.then((int exitCode) {
         print('${arguments.join(" ")} exited with $exitCode');
       });
       debuggerMain();
     });
   } else {
     debuggerMain();
   }
 }