Migrate language/arithmetic2_test ... language/async_await_syntax_test.

tests/language/assign_instance_method_negative_test.dart

Index: tests/language/assign_instance_method_negative_test.dart
diff --git a/tests/language/assign_instance_method_negative_test.dart b/tests/language/assign_instance_method_negative_test.dart
deleted file mode 100644
index 0e17f16aa7dccb8405498341fa6dc6c586f8ad3c..0000000000000000000000000000000000000000
--- a/tests/language/assign_instance_method_negative_test.dart
+++ /dev/null
@@ -1,18 +0,0 @@
-// 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.
-
-class A {
-  A() {}
-  imethod() {
-    return 0;
-  }
-}
-
-main() {
-  var a = new A();
-  // Illegal, can't change a member method
-  a.imethod = () {
-    return 1;
-  };
-}