Extract CallStructure from Selector.

tests/language/private_access_lib.dart

Index: tests/language/private_access_lib.dart
diff --git a/runtime/observatory/lib/cli.dart b/tests/language/private_access_lib.dart
similarity index 71%
copy from runtime/observatory/lib/cli.dart
copy to tests/language/private_access_lib.dart
index 607c58a919685c7fca635c1bf5acb02543720582..e9af62079d42b01f3f0ca4a9e4a055426a6ad53a 100644
--- a/runtime/observatory/lib/cli.dart
+++ b/tests/language/private_access_lib.dart
@@ -2,8 +2,12 @@
 // 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.
 
-library cli;
+library private;
 
-import 'dart:async';
+_function() {}
 
-part 'src/cli/command.dart';
+class _Class {}
+
+class Class {
+  Class._constructor();
+}