Backup includes for PTRACE_GET_THREAD_AREA

PTRACE_GET_THREAD_AREA is not in ptrace.h in Ubuntu 16.04 when
building for Linux without a sysroot so get it from somewhere else,
in this case asm/ptrace-abi.h.

Follow up to https://chromium-review.googlesource.com/c/1479092

Bug: 934238,933418
Change-Id: I3e1ace31a6f5a4ab65bbe712e1516d7b5fa009a5
Reviewed-on: https://chromium-review.googlesource.com/c/1481316
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#634660}
diff --git a/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.cc b/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.cc
index ecd6e339..55394a7 100644
--- a/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.cc
+++ b/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.cc
@@ -34,7 +34,13 @@
 #if !defined(OS_NACL_NONSFI)
 #include <sys/ioctl.h>
 #include <sys/ptrace.h>
-#endif
+#if !defined(PTRACE_GET_THREAD_AREA) && defined(OS_LINUX) && \
+    !defined(OS_CHROMEOS)
+// Also include asm/ptrace-abi.h since ptrace.h in older libc (for instance
+// the one in Ubuntu 16.04 LTS) is missing PTRACE_GET_THREAD_AREA.
+#include <asm/ptrace-abi.h>
+#endif  // !PTRACE_GET_THREAD_AREA && OS_LINUX && !OS_CHROMEOS
+#endif  // !OS_NACL_NONSFI
 
 #if defined(OS_ANDROID)