Linux: add basic unprivileged namespace support.

sandbox/linux/tests/main.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/at_exit.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 int main(int argc, char *argv[]) {
+  // The use of Callbacks requires an AtExitManager.
+  base::AtExitManager exit_manager;
   testing::InitGoogleTest(&argc, argv);
   // Always go through re-execution for death tests.
   // This makes gtest only marginally slower for us and has the
   // additional side effect of getting rid of gtest warnings about fork()
   // safety.
   ::testing::FLAGS_gtest_death_test_style = "threadsafe";
   return RUN_ALL_TESTS();
 }