Revert "Remove Expect from core library."

tests/language/inline_getter_test.dart

 // Copyright (c) 2011, 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 inlining of instance getters.
 // Three classes access always the same field. Optimize method foo and inline
 // getter for classes 'A' and 'B'. Call later via 'C' and cause deoptimization.
 
-import "package:expect/expect.dart";
-
 class A {
   int f;
   A(this.f) {}
   int foo() {
     return f;  // <-- inline getter for classes 'A' and 'B'.
   }
 }
 
 class B extends A {
   B() : super(2) {}
@@ skipping 14 matching lines @@
     }
     var c = new C();
     sum += c.foo();  // <-- Deoptimizing.
     Expect.equals(15010, sum);
   }
 }
 
 main() {
   InlineGetterTest.testMain();
 }