Fix more test imports

tests/compiler/dart2js_native/native_class_fields_3_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.
 
+import "package:expect/expect.dart";
+
 // Verify that we can have fields with names that start with g and s even
 // though those names are reserved for getters and setters in minified mode.
 
 // Note: this works because end and send are both in the list of
 // reservedNativeProperties.  In general we don't check arbitrary
 // names for clashes because it's hard - subclasses can force superclasses
 // to rename getters, and that can force unrelated classes to change their
 // getters too if they have a property that has the same name.
 class A native "*A" {
   int bar;
@@ skipping 62 matching lines @@
   Expect.equals(42, foo.send);
   Expect.equals(271, foo.bar = 271);
   Expect.equals(271, foo.g = 271);
   Expect.equals(271, foo.s = 271);
   Expect.equals(271, foo.end = 271);
   Expect.equals(271, foo.gend = 271);
   Expect.equals(271, foo.send = 271);
   Expect.equals(6, foo.gettersCalled);
   Expect.equals(6, foo.settersCalled);
 }
-