Delete unused file.

utils/apidoc/scripts/list_files.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.
-
-/**
- * Traverses apidoc and dartdoc and lists all possible input files that are
- * used when building API documentation. Used by gyp to determine when apidocs
- * need to be regenerated (see `apidoc.gyp`).
- */
-library list_files;
-
-import 'dart:io';
-
-const allowedExtensions = const [
-  '.css', '.dart', '.ico', '.js', '.json', '.png', '.sh', '.txt'
-];
-
-void main() {
-  final scriptDir = new File(new Options().script).directorySync().path;
-  final dartDir = '$scriptDir/../../../';
-  listFiles('$dartDir/utils/apidoc');
-  listFiles('$dartDir/sdk/lib/_internal/dartdoc');
-}
-
-void listFiles(String dirPath) {
-  final dir = new Directory(dirPath);
-
-  dir.onFile = (path) {
-    if (allowedExtensions.indexOf(extension(path)) != -1) {
-      print(path);
-    }
-  };
-
-  dir.list(recursive: true);
-}
-
-String extension(String path) {
-  int lastDot = path.lastIndexOf('.');
-  if (lastDot == -1) return '';
-
-  return path.substring(lastDot);
-}