Revert "Remove Expect from core library."

tests/standalone/io/dart_std_io_pipe_test.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.
 //
 // Test a dart sub-process handling stdio with different types of
 // redirection.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
-import "package:expect/expect.dart";
 import "dart:io";
 import "process_test_util.dart";
 
 void checkFileEmpty(String fileName) {
   RandomAccessFile pipeOut  = new File(fileName).openSync();
   Expect.equals(0, pipeOut.lengthSync());
   pipeOut.closeSync();
 }
 
 
@@ skipping 71 matching lines @@
   var scriptFile = new File("tests/standalone/io/process_std_io_script.dart");
   if (!scriptFile.existsSync()) {
     scriptFile = new File("../tests/standalone/io/process_std_io_script.dart");
   }
 
   // Run the shell script.
   test(shellScript.path, scriptFile.path, "0");
   test(shellScript.path, scriptFile.path, "1");
   test(shellScript.path, scriptFile.path, "2");
 }