Update from https://crrev.com/316786

sandbox/linux/services/namespace_utils.h

 // Copyright 2015 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.
 
 #ifndef SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
 #define SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
 
 #include <sys/types.h>
 
 #include "base/compiler_specific.h"
@@ skipping 15 matching lines @@
   static bool WriteToIdMapFile(const char* map_file,
                                generic_id_t id) WARN_UNUSED_RESULT;
 
   // 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 sandbox.
   static bool KernelSupportsUnprivilegedNamespace(int type);
 
+  // Returns true if the kernel supports denying setgroups in a user namespace.
+  // On kernels where this is supported, DenySetgroups must be called before a
+  // gid mapping can be added.
+  static bool KernelSupportsDenySetgroups();
+
+  // Disables setgroups() within the current user namespace. On Linux 3.18.2 and
+  // later, this is required in order to write to /proc/self/gid_map without
+  // having CAP_SETGID. Callers can determine whether is this needed with
+  // KernelSupportsDenySetgroups. This function is async-signal-safe.
+  static bool DenySetgroups() WARN_UNUSED_RESULT;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(NamespaceUtils);
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_