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diff --git a/security/sandbox/chromium/base/posix/can_lower_nice_to.cc b/security/sandbox/chromium/base/posix/can_lower_nice_to.cc
new file mode 100644
index 0000000000..b1686dcae1
--- /dev/null
+++ b/security/sandbox/chromium/base/posix/can_lower_nice_to.cc
@@ -0,0 +1,60 @@
+// Copyright 2018 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 "base/posix/can_lower_nice_to.h"
+
+#include <limits.h>
+#include <sys/resource.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "build/build_config.h"
+
+// Not defined on AIX by default.
+#if defined(OS_AIX)
+#if defined(RLIMIT_NICE)
+#error Assumption about OS_AIX is incorrect
+#endif
+#define RLIMIT_NICE 20
+#endif
+
+namespace base {
+namespace internal {
+
+bool CanLowerNiceTo(int nice_value) {
+  // On a POSIX system, the nice value of a thread can be lowered 1. by the root
+  // user, 2. by a user with the CAP_SYS_NICE permission or 3. by any user if
+  // the target value is within the range allowed by RLIMIT_NICE.
+
+  // 1. Check for root user.
+  if (geteuid() == 0)
+    return true;
+
+  // 2. Skip checking the CAP_SYS_NICE permission because it would require
+  // libcap.so.
+
+  // 3. Check whether the target value is within the range allowed by
+  // RLIMIT_NICE.
+  //
+  // NZERO should be defined in <limits.h> per POSIX, and should be at least 20.
+  // (NZERO-1) is the highest possible niceness value (i.e. lowest priority).
+  // Most platforms use NZERO=20.
+  //
+  // RLIMIT_NICE tells us how much we can reduce niceness (increase priority) if
+  // we start at NZERO. For example, if NZERO is 20 and the rlimit is 30, we can
+  // lower niceness anywhere within the [-10, 19] range (20 - 30 = -10).
+  //
+  // So, we are allowed to reduce niceness to a minimum of NZERO - rlimit:
+  struct rlimit rlim;
+  if (getrlimit(RLIMIT_NICE, &rlim) != 0)
+    return false;
+  const int lowest_nice_allowed = NZERO - static_cast<int>(rlim.rlim_cur);
+
+  // And lowering niceness to |nice_value| is allowed if it is greater than or
+  // equal to the limit:
+  return nice_value >= lowest_nice_allowed;
+}
+
+}  // namespace internal
+}  // namespace base