Use the suid helper for oom_score_adj on Chrome OS.

content/browser/zygote_host/zygote_communication_linux.cc

 // 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.
 
 #include "content/browser/zygote_host/zygote_communication_linux.h"
 
 #include <string.h>
 #include <sys/socket.h>
 
 #include "base/base_switches.h"
@@ skipping 285 matching lines @@
   GetContentClient()->browser()->AppendExtraCommandLineSwitches(&cmd_line, -1);
 
   const bool using_namespace_sandbox = ShouldUseNamespaceSandbox();
   // A non empty sandbox_cmd means we want a SUID sandbox.
   const bool using_suid_sandbox =
       !ZygoteHostImpl::GetInstance()->SandboxCommand().empty() &&
       !using_namespace_sandbox;
   // Use the SUID sandbox for adjusting OOM scores when we are using the setuid
   // or namespace sandbox. This is needed beacuse the processes are
   // non-dumpable, so /proc/pid/oom_score_adj can only be written by root.
-  use_suid_sandbox_for_adj_oom_score_ =
-      !ZygoteHostImpl::GetInstance()->SandboxCommand().empty() &&
-      using_suid_sandbox;
+  use_suid_sandbox_for_adj_oom_score_ = using_suid_sandbox;
+
+#if defined(OS_CHROMEOS)
+  // Chrome OS has a kernel patch that restricts oom_score_adj. See
+  // crbug.com/576409 for details.
+  if (!ZygoteHostImpl::GetInstance()->SandboxCommand().empty() &&
+      using_namespace_sandbox) {
+    use_suid_sandbox_for_adj_oom_score_ = true;
+  }
+#endif
 
   // Start up the sandbox host process and get the file descriptor for the
   // renderers to talk to it.
   const int sfd = RenderSandboxHostLinux::GetInstance()->GetRendererSocket();
   fds_to_map.push_back(std::make_pair(sfd, GetSandboxFD()));
 
   base::ScopedFD dummy_fd;
   if (using_suid_sandbox) {
     scoped_ptr<sandbox::SetuidSandboxHost> sandbox_host(
         sandbox::SetuidSandboxHost::Create());
@@ skipping 132 matching lines @@
   }
   if (ReadSandboxStatus() == -1) {
     return 0;
   }
   have_read_sandbox_status_word_ = true;
   UMA_HISTOGRAM_SPARSE_SLOWLY("Linux.SandboxStatus", sandbox_status_);
   return sandbox_status_;
 }
 
 }  // namespace content