Remove Expect from core library.

tests/compiler/dart2js/interceptor_test.dart

 // Copyright (c) 2013, 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 'compiler_helper.dart';
 
 const String TEST_ONE = r"""
   foo(a) {
     // Make sure there is a bailout version.
     foo(a);
     // This will make a one shot interceptor that will be optimized in
     // the non-bailout version because we know a is a number.
     return (a + 42).toString;
   }
@@ skipping 30 matching lines @@
   Expect.isTrue(generated.contains('myVariableName'));
 
   // Check that an intercepted getter that does not need to be
   // intercepted, is turned into a regular getter call or field
   // access.
   generated = compile(TEST_THREE, entry: 'foo');
   Expect.isFalse(generated.contains(r'get$length'));
   Expect.isTrue(generated.contains(r'$.A$().length'));
   Expect.isTrue(generated.contains(r'length(a)'));
 }