Revert "Remove Expect from core library."

tests/compiler/dart2js/resolver_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.
 
-import "package:expect/expect.dart";
 import 'dart:collection';
 
 import "../../../sdk/lib/_internal/compiler/implementation/resolution/resolution.dart";
 import "compiler_helper.dart";
 import "parser_helper.dart";
 
 import '../../../sdk/lib/_internal/compiler/implementation/dart_types.dart';
 
 Node buildIdentifier(String name) => new Identifier(scan(name));
 
@@ skipping 820 matching lines @@
         var d = new D();
         --d;
       }""";
   final compiler = compileScript(script);
 
   checkMemberResolved(compiler, 'A', operatorName('+', false));
   checkMemberResolved(compiler, 'B', operatorName('+', false));
   checkMemberResolved(compiler, 'C', operatorName('-', false));
   checkMemberResolved(compiler, 'D', operatorName('-', false));
 }