Remove Expect from core library.

tests/compiler/dart2js_extra/bailout_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";
+
 var myString;
 
 String ifBailout(test) {
   if (test) {
     // Share the same variable for the type inference.
     var o = myString;
     // Make sure the type inference wants an array.
     if (false) o[1] = 2;
     return '${o[0]} bailout';
   }
@@ skipping 195 matching lines @@
   Expect.equals('1234', doWhileBailout());
 
   Expect.equals(102334155, fibonacci(40));
 
   phiBailout();
   ifPhiBailout1(1);
   ifPhiBailout1(2);
   ifPhiBailout2(1);
   ifPhiBailout2(2);
 }