Update from https://crrev.com/316786

sandbox/linux/services/proc_util.h

 // Copyright 2014 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_PROC_UTIL_H_
 #define SANDBOX_LINUX_SERVICES_PROC_UTIL_H_
 
+#include "base/files/scoped_file.h"
 #include "base/macros.h"
 #include "sandbox/sandbox_export.h"
 
 namespace sandbox {
 
 class SANDBOX_EXPORT ProcUtil {
  public:
   // Returns the number of file descriptors in the current process's FD
   // table, excluding |proc_fd|, which should be a file descriptor for
   // /proc.
   static int CountOpenFds(int proc_fd);
 
   // Checks whether the current process has any directory file descriptor open.
   // Directory file descriptors are "capabilities" that would let a process use
   // system calls such as openat() to bypass restrictions such as
   // DropFileSystemAccess().
   // Sometimes it's useful to call HasOpenDirectory() after file system access
   // has been dropped. In this case, |proc_fd| should be a file descriptor to
   // /proc. The file descriptor in |proc_fd| will be ignored by
   // HasOpenDirectory() and remains owned by the caller. It is very important
   // for the caller to close it.
   // If /proc is available, |proc_fd| can be passed as -1.
   // If |proc_fd| is -1 and /proc is not available, this function will return
   // false.
   static bool HasOpenDirectory(int proc_fd);
 
+  // Open /proc/self/task/ or crash if it cannot.
+  static base::ScopedFD OpenProcSelfTask();
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ProcUtil);
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_PROC_UTIL_H_