Revert "Remove Expect from core library."

tests/standalone/io/file_input_stream_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.
 // Testing file input stream, VM-only, standalone test.
 
-import "package:expect/expect.dart";
 import "dart:io";
 import "dart:isolate";
 
 // Helper method to be able to run the test from the runtime
 // directory, or the top directory.
 String getFilename(String path) =>
     new File(path).existsSync() ? path : '../$path';
 
 void testStringLineTransformer() {
   String fileName = getFilename("tests/standalone/io/readuntil_test.dat");
@@ skipping 180 matching lines @@
   testOpenStreamAsync();
   testInputStreamTruncate();
   testInputStreamDelete();
   testInputStreamAppend();
   // Check the length of these files as both are text files where one
   // is without a terminating line separator which can easily be added
   // back if accidentally opened in a text editor.
   testStringLineTransformerEnding("readline_test1.dat", 111);
   testStringLineTransformerEnding("readline_test2.dat", 114);
 }