Private names are not exported, not even if the library imports itself

tests/language/import_self_test.dart

+// Copyright (c) 2014, 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.
+//
+// Check that private names cannot be imported even if the library imports
+// itself.
+
+library import_self;
+
+import "package:expect/expect.dart";
+
+// Eliminate the import of the unmodified file or else the analyzer
+// will generate the static warning in the import_self_test_none case.
+import "import_self_test.dart" as p;  /// 01: continued
+
+var _x = "The quick brown fox jumps over the dazy log";
+
+main() {
+  var t = "Falsches Üben von Xylophonmusik quält jeden größeren Zwerg";
+
+  // Check that referencing p._x causes a warning from the analyzer,
+  // and the runtime fails to resolve p._x, even though it refers to
+  // top level variable _x of this file.
+  Expect.throws(() { t = p._x; },  /// 01: static type warning
+                (e) => e is NoSuchMethodError);  /// 01: continued
+
+  Expect.isTrue(t.endsWith("Zwerg"));
+}