Remove Expect from core library.

tests/compiler/dart2js/analyze_only_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.
 
 // Smoke test of the dart2js compiler API.
 library analyze_only;
 
+import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:uri';
 
 import '../../utils/dummy_compiler_test.dart' as dummy;
 import '../../../sdk/lib/_internal/compiler/compiler.dart';
 
 runCompiler(String main, List<String> options,
             onValue(String code, List errors, List warnings)) {
   List errors = new List();
   List warnings = new List();
@@ skipping 102 matching lines @@
     """Foo foo; // Unresolved and analyzed.
        main() {}""",
     ['--analyze-only', '--analyze-all'],
     (String code, List errors, List warnings) {
       Expect.isNull(code);
       Expect.isTrue(errors.isEmpty);
       Expect.equals(1, warnings.length);
       Expect.equals('Warning: cannot resolve type Foo', warnings[0].toString());
     });
 }