Convert use_seccomp_bpf to the BUILDFLAG system.

chrome/browser/android/seccomp_support_detector.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 "chrome/browser/android/seccomp_support_detector.h"
 
 #include <stdio.h>
 #include <sys/utsname.h>
 
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "content/public/browser/browser_thread.h"
+#include "sandbox/sandbox_features.h"
 
-#if defined(USE_SECCOMP_BPF)
+#if BUILDFLAG(USE_SECCOMP_BPF)
 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
 #endif
 
 using content::BrowserThread;
 
 enum AndroidSeccompStatus {
   // DETECTION_FAILED was formerly used when probing for seccomp was done
   // out-of-process. There does not appear to be a gain in doing so, as
   // explained in the comment in DetectSeccomp(). This enum remains for
   // historical reasons.
@@ skipping 35 matching lines @@
     if (sscanf(uts.release, "%d.%d", &major, &minor) == 2) {
       int version = ((major & 0xFFFF) << 16) | (minor & 0xFFFF);
       UMA_HISTOGRAM_SPARSE_SLOWLY("Android.KernelVersion", version);
     }
   }
 }
 
 void SeccompSupportDetector::DetectSeccomp() {
   DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
 
-#if defined(USE_SECCOMP_BPF)
+#if BUILDFLAG(USE_SECCOMP_BPF)
   bool prctl_supported = sandbox::SandboxBPF::SupportsSeccompSandbox(
       sandbox::SandboxBPF::SeccompLevel::SINGLE_THREADED);
 #else
   bool prctl_supported = false;
 #endif
 
   UMA_HISTOGRAM_ENUMERATION("Android.SeccompStatus.Prctl",
                             prctl_supported ? SUPPORTED : NOT_SUPPORTED,
                             LAST_STATUS);
 
   // Probing for the seccomp syscall can provoke kernel panics in certain LGE
   // devices. For now, this data will not be collected. In the future, this
   // should detect SeccompLevel::MULTI_THREADED. http://crbug.com/478478
 }