Move tools to tool folder.

pkg/front_end/tool/_fasta/dump_partial.dart

 // Copyright (c) 2017, 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.
 
 /// Utility to dump a truncated .dill file generated by the incremental kernel
 /// generator or by the VM's kernel service.
 import 'dart:io';
 import 'package:kernel/kernel.dart';
 import 'package:front_end/src/fasta/kernel/utils.dart';
 
 main(List<String> args) {
   if (args.length == 0) {
     print('usage: pkg/front_end/tool/fasta dump_partial '
         'partial.dill [extra1.dill] ... [extraN.dill]');
     exitCode = 1;
+    return;
   }
 
   var program = _loadProgram(args);
   writeProgramToText(program);
 }
 
 /// Creates a program that contains all of the context code marked as external,
 /// and all libraries defined in partial.dill as they are written in that file.
 Program _loadProgram(List<String> args) {
   List<int> partialInput = new File(args[0]).readAsBytesSync();
@@ skipping 37 matching lines @@
       .where((l) => !l.isExternal)
       .map((l) => l.importUri)
       .toSet();
   _updateIsExternal(context, false);
   return result;
 }
 
 void _updateIsExternal(Program program, bool toValue) {
   program.libraries.forEach((lib) => lib.isExternal = toValue);
 }