Revert "Remove Expect from core library."

tests/compiler/dart2js_native/native_call_arity1_frog_test.dart

Index: tests/compiler/dart2js_native/native_call_arity1_frog_test.dart
diff --git a/tests/compiler/dart2js_native/native_call_arity1_frog_test.dart b/tests/compiler/dart2js_native/native_call_arity1_frog_test.dart
index 6f398b43fe62bcefd0419004ebc20c3fe514836e..8558b2290de3bfbb1ba90d9dfb904fa6de4ee039 100644
--- a/tests/compiler/dart2js_native/native_call_arity1_frog_test.dart
+++ b/tests/compiler/dart2js_native/native_call_arity1_frog_test.dart
@@ -2,8 +2,6 @@
 // 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";
-
 // Test that native methods with unnamed* optional arguments are called with the
 // number of arguments in the call site.  This is necessary because native
 // methods can dispatch on the number of arguments.  Passing null or undefined