Move tools to tool folder.

pkg/front_end/tool/bazel/worker.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.
 import 'dart:async';
 import 'dart:io';
 
 import 'package:args/args.dart';
 import 'package:bazel_worker/bazel_worker.dart';
 import 'package:front_end/front_end.dart' hide FileSystemException;
 import 'package:front_end/src/fasta/command_line_reporting.dart';
@@ skipping 80 matching lines @@
 
   if (outputBuffer != null) {
     options.onError = (CompilationMessage error) {
       var severityString = severityName(error.severity, capitalized: true);
       outputBuffer.writeln('$severityString: ${error.message}');
       if (error.severity != Severity.nit) {
         throw error;
       }
     };
   } else {
-    options.throwOnWarnings = true;
+    options.throwOnWarningsForDebugging = true;
   }
 
   var sources = parsedArgs['source'].map(Uri.parse).toList();
   var program = await summaryFor(sources, options);
 
   var outputFile = new File(parsedArgs['output']);
   outputFile.createSync(recursive: true);
   outputFile.writeAsBytesSync(program);
 }