Update from https://crrev.com/311145

sandbox/linux/suid/client/setuid_sandbox_client.cc

 // 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.
 
 #include "sandbox/linux/suid/client/setuid_sandbox_client.h"
 
 #include <fcntl.h>
 #include <stdlib.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
@@ skipping 190 matching lines @@
     return false;
   }
 
   // We now consider ourselves "fully sandboxed" as far as the
   // setuid sandbox is concerned.
   CHECK(IsFileSystemAccessDenied());
   sandboxed_ = true;
   return true;
 }
 
-bool SetuidSandboxClient::CreateNewSession() {
-  // This could fail if the process is already a process group leader.
-  return 0 < setsid();
-}
-
 bool SetuidSandboxClient::CreateInitProcessReaper(
     base::Closure* post_fork_parent_callback) {
   return sandbox::CreateInitProcessReaper(post_fork_parent_callback);
 }
 
 bool SetuidSandboxClient::IsSuidSandboxUpToDate() const {
   return GetHelperApi(env_) == kSUIDSandboxApiNumber;
 }
 
 bool SetuidSandboxClient::IsSuidSandboxChild() const {
@@ skipping 89 matching lines @@
   // kZygoteIdFd. Fixing this requires a sandbox API change. :(
   fds_to_remap->push_back(std::make_pair(dummy_fd->get(), kZygoteIdFd));
 }
 
 void SetuidSandboxClient::SetupLaunchEnvironment() {
   SaveSUIDUnsafeEnvironmentVariables(env_);
   SetSandboxAPIEnvironmentVariable(env_);
 }
 
 }  // namespace sandbox