Calling clone(CLONE_NEWPID) results in the new pid namespace getting a new "init" process.

sandbox/sandbox.gyp

 # Copyright (c) 2011 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'target_defaults': {
     'variables': {
@@ skipping 137 matching lines @@
           ],
         },
       ],
     }],
     [ 'OS=="linux" and selinux==0', {
       'targets': [
         {
           'target_name': 'chrome_sandbox',
           'type': 'executable',
           'sources': [
+            'linux/suid/init_process.c',
+            'linux/suid/init_process.h',
             'linux/suid/linux_util.c',
             'linux/suid/linux_util.h',
             'linux/suid/process_util.h',
             'linux/suid/process_util_linux.c',
             'linux/suid/sandbox.c',
           ],
           'cflags': [
             # For ULLONG_MAX
             '-std=gnu99',
           ],
@@ skipping 204 matching lines @@
             'POCDLL_EXPORTS',
           ],
           'include_dirs': [
             '..',
           ],
         },
       ],
     }],
   ],
 }