Convert use_seccomp_bpf to the BUILDFLAG system.

content/renderer/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//media/media_options.gni")
 import("//ppapi/features/features.gni")
 import("//printing/features/features.gni")
 import("//third_party/webrtc/build/webrtc.gni")
@@ skipping 875 matching lines @@
     ]
 
     deps += [
       "//media/mojo/interfaces",
 
       # Defines in mojo_media_config are also pulled in here.
       "//media/mojo/clients",
     ]
   }
 
-  if (use_seccomp_bpf) {
-    defines += [ "USE_SECCOMP_BPF" ]
+  if (is_linux || is_android) {
+    deps += [ "//sandbox:sandbox_features" ]
   }
 
   if (use_ozone) {
     deps += [ "//ui/ozone" ]
   }
 
   if (enable_ipc_fuzzer) {
     configs += [ "//tools/ipc_fuzzer:ipc_fuzzer_config" ]
   }
 }
 
 # See comment at the top of //content/BUILD.gn for how this works.
 group("for_content_tests") {
   visibility = [ "//content/test/*" ]
 
   if (enable_mojo_media) {
     # For the defines in mojo_media_config.
     public_configs = [ "//media/mojo/services:mojo_media_config" ]
   }
 
   if (!is_component_build) {
     public_deps = [
       ":renderer",
     ]
   }
 }