Remove Expect from core library.

tests/language/argument_definition_test.dart

Index: tests/language/argument_definition_test.dart
diff --git a/tests/language/argument_definition_test.dart b/tests/language/argument_definition_test.dart
index 14d7e6df6f15a712c41109e6bbdc2e82aa3136ba..31d8431de15c7e71f7e6b8bb68628091d14eeffb 100644
--- a/tests/language/argument_definition_test.dart
+++ b/tests/language/argument_definition_test.dart
@@ -3,6 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 // Dart test program for testing argument definition test.
 
+import "package:expect/expect.dart";
+
 int test(int a, {int b: 2, int c: 3}) {
   int result = 0;
   ?b;