Remove package imports from itself.

utils/kernel-service/kernel-service.dart

 // Copyright (c) 2016, 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.
 
 /// This is an interface to the Dart Kernel parser and Kernel binary generator.
 ///
 /// It is used by the kernel-isolate to load Dart source code and generate
 /// Kernel binary format.
 ///
 /// This is either invoked as the root script of the Kernel isolate when used
 /// as a part of
 ///
 ///         dart --dfe=utils/kernel-service/kernel-service.dart ...
 ///
 /// invocation or it is invoked as a standalone script to perform training for
 /// the app-jit snapshot
 ///
 ///         dart utils/kernel-service/kernel-service.dart --train <source-file>
 ///
 ///
 library runtime.tools.kernel_service;
 
 import 'dart:async';
-import 'dart:convert';
 import 'dart:io';
 import 'dart:isolate';
 import 'dart:typed_data';
 
 import 'package:kernel/binary/ast_to_binary.dart';
 import 'package:kernel/kernel.dart';
 import 'package:kernel/target/targets.dart';
 
 import 'package:front_end/src/fasta/dill/dill_target.dart' show DillTarget;
 import 'package:front_end/src/fasta/translate_uri.dart' show TranslateUri;
@@ skipping 236 matching lines @@
     if (await new File.fromUri(packagesFile).exists()) {
       return packagesFile;
     }
     if (dir.parent.path == dir.path) {
       break;
     }
     dir = dir.parent;
   }
   return null;
 }