Removed fixed dependencies

packages/crypto/example/hash.dart

+// Copyright (c) 2015, 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:crypto/crypto.dart';
+
+final _usage = 'Usage: dart hash.dart <md5|sha1|sha256> <input_filename>';
+
+Future main(List<String> args) async {
+  if (args == null || args.length != 2) {
+    print(_usage);
+    exit(1);
+  }
+
+  Hash hasher;
+
+  switch (args[0]) {
+    case 'md5':
+      hasher = md5;
+      break;
+    case 'sha1':
+      hasher = sha1;
+      break;
+    case 'sha256':
+      hasher = sha256;
+      break;
+    default:
+      print(_usage);
+      exit(1);
+  }
+
+  var filename = args[1];
+  var input = new File(filename);
+
+  if (!input.existsSync()) {
+    print('File "$filename" does not exist.');
+    exit(1);
+  }
+
+  var value = await hasher.bind(input.openRead()).first;
+
+  print(value);
+}