Move a couple of utility functions to a new namespace_utils class.

sandbox/linux/services/namespace_utils.h

Index: sandbox/linux/services/namespace_utils.h
diff --git a/sandbox/linux/services/namespace_utils.h b/sandbox/linux/services/namespace_utils.h
new file mode 100644
index 0000000000000000000000000000000000000000..98997f2868a8475d09e61d4d5a3d3ca08d4276a0
--- /dev/null
+++ b/sandbox/linux/services/namespace_utils.h
@@ -0,0 +1,39 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.

[jln (very slow on Chromium), 2015/01/27 00:06:44]

2015

[rickyz (no longer on Chrome), 2015/01/27 01:08:03]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
+#define SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
+
+#include <sys/types.h>
+
+#include "base/macros.h"
+#include "base/template_util.h"
+#include "sandbox/sandbox_export.h"
+
+namespace sandbox {
+
+// Utility functions for using Linux namepaces.
+class SANDBOX_EXPORT NamespaceUtils {
+ public:
+  COMPILE_ASSERT((base::is_same<uid_t, gid_t>::value), UidAndGidAreSameType);
+  // generic_id_t can be used for either uid_t or gid_t.
+  typedef uid_t generic_id_t;
+
+  // Write a uid or gid mapping from |id| to |id| in |map_file|.
+  static bool WriteToIdMapFile(const char* map_file, generic_id_t id);
+
+  // Returns true if unprivileged namespaces of type |type| is supported
+  // (meaning that both CLONE_NEWUSER and type are are supported).  |type| must
+  // be one of CLONE_NEWIPC, CLONE_NEWNET, CLONE_NEWNS, CLONE_NEWPID,
+  // CLONE_NEWUSER, or CLONE_NEWUTS. This relies on access to /proc, so it will
+  // not work from within a chroot.

[jln (very slow on Chromium), 2015/01/27 00:06:44]

Nite: maybe s/chroot/sandbox to be more generic?

[rickyz (no longer on Chrome), 2015/01/27 01:08:03]

Done.

+  static bool KernelSupportsUnprivilegedNamespace(int type);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(NamespaceUtils);
+};
+
+}  // namespace sandbox
+
+#endif  // SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_