Revert "Remove Expect from core library."

tests/compiler/dart2js/class_codegen2_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 that parameters keep their names in the output.
 
-import "package:expect/expect.dart";
 import 'compiler_helper.dart';
 import 'parser_helper.dart';
 
 const String TEST_ONE = r"""
 class A { foo() => 499; }
 class B { bar() => 42; }
 
 main() {
   new A().foo();
   new B().bar();
@@ skipping 75 matching lines @@
 
   generated = compileAll(TEST_TWO);
   Expect.isFalse(danglingComma.hasMatch(generated));
 
   generated = compileAll(TEST_THREE);
   Expect.isFalse(danglingComma.hasMatch(generated));
 
   generated = compileAll(TEST_FOUR);
   Expect.isFalse(danglingComma.hasMatch(generated));
 }