Remove Expect from core library.

tests/language/megamorphic_no_such_method_test.dart

Index: tests/language/megamorphic_no_such_method_test.dart
diff --git a/tests/language/megamorphic_no_such_method_test.dart b/tests/language/megamorphic_no_such_method_test.dart
index 56c3287a3b1586ab6200961546eb9de631ca1f57..8d7976af9ec8fce9e5aba81a323ea109b1b959eb 100644
--- a/tests/language/megamorphic_no_such_method_test.dart
+++ b/tests/language/megamorphic_no_such_method_test.dart
@@ -3,6 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 // Test program for correct optimizations related to types fo allocated lists.
 
+import "package:expect/expect.dart";
+
 // Classes to induce polymorphism of degree 10.
 class A0 {
   test() => 0;