Update from https://crrev.com/314320

sandbox/linux/sandbox_linux.gypi

 # 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.
 
 {
   'variables': {
     'conditions': [
       ['OS=="linux"', {
         'compile_suid_client': 1,
         'compile_credentials': 1,
@@ skipping 236 matching lines @@
         '../base/base.gyp:base',
       ],
       'defines': [
         'SANDBOX_IMPLEMENTATION',
       ],
       'conditions': [
         ['compile_credentials==1', {
           'sources': [
             'services/credentials.cc',
             'services/credentials.h',
+            'services/namespace_sandbox.cc',
+            'services/namespace_sandbox.h',
             'services/namespace_utils.cc',
             'services/namespace_utils.h',
             'services/proc_util.cc',
             'services/proc_util.h',
           ],
           'dependencies': [
             # for capabilities.cc.
             '../build/linux/system.gyp:libcap',
           ],
         }],
@@ skipping 119 matching lines @@
             '../../build/isolate.gypi',
           ],
           'sources': [
             '../sandbox_linux_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }