Ensure that unmangled private names are unique.

tests/lib/mirrors/private_symbol_mangling_lib.dart

Index: tests/lib/mirrors/private_symbol_mangling_lib.dart
diff --git a/tests/language/regress_18865_test.dart b/tests/lib/mirrors/private_symbol_mangling_lib.dart
similarity index 62%
copy from tests/language/regress_18865_test.dart
copy to tests/lib/mirrors/private_symbol_mangling_lib.dart
index ba64c4c9f51fff6ae2bc2e4f1605a8c0808ef472..8d9c93bb0bd252a8ae0fb1f11282fa0c0763e7ae 100644
--- a/tests/language/regress_18865_test.dart
+++ b/tests/lib/mirrors/private_symbol_mangling_lib.dart
@@ -2,14 +2,13 @@
 // 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.
 
-// Regression test for issue 18865.
+library other;
 
-class B<T> { }
+var _privateGlobalField = 3;
 
-class A<T> extends B {
-  static foo() => new A();
-}
+_privateGlobalMethod() => 11;
 
-main () {
-  A.foo();
+class C2 {
+  var _privateField = 1;
+  _privateMethod() => 3;
 }