Convert use_seccomp_bpf to the BUILDFLAG system.

chrome/browser/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/chrome_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/split_static_library.gni")
 import("//chrome/common/features.gni")
 import("//components/os_crypt/features.gni")
 import("//components/spellcheck/spellcheck_build_features.gni")
 import("//extensions/features/features.gni")
 import("//media/media_options.gni")
 import("//net/features.gni")
 import("//ppapi/features/features.gni")
 import("//printing/features/features.gni")
+import("//sandbox/features.gni")
 import("//third_party/protobuf/proto_library.gni")
 import("//ui/base/ui_features.gni")
 
 # //build/config/android/rules.gni imports //tools/grit/grit_rule.gni, which
 # produces a conflict for the "grit" template so we have to only include one.
 if (is_android) {
   import("//build/config/android/rules.gni")
 } else {
   import("//tools/grit/grit_rule.gni")
 }
@@ skipping 2557 matching lines @@
     sources += [
       "chrome_browser_field_trials_mobile.cc",
       "chrome_browser_field_trials_mobile.h",
       "policy/cloud/user_policy_signin_service_mobile.cc",
       "policy/cloud/user_policy_signin_service_mobile.h",
     ]
     deps += [
       "//components/cdm/browser",
       "//components/payments/android:payments_jni",
       "//components/resources:components_resources",
+      "//sandbox:sandbox_features",
       "//third_party/android_opengl/etc1",
       "//third_party/android_tools:cpu_features",
       "//third_party/libaddressinput:util",
     ]
 
     deps -= [ "//components/storage_monitor" ]
     if (use_seccomp_bpf) {
-      defines += [ "USE_SECCOMP_BPF" ]
       deps += [ "//sandbox/linux:seccomp_bpf" ]
     }
   } else {
     # Non-Android.
     sources += [
       "accessibility/invert_bubble_prefs.cc",
       "accessibility/invert_bubble_prefs.h",
       "background/background_contents.cc",
       "background/background_contents.h",
       "banners/app_banner_infobar_delegate_desktop.cc",
@@ skipping 1838 matching lines @@
   # linking all of the test support.
   static_library("pepper_cdm_test_constants") {
     testonly = true
     visibility = [ "//chrome/*" ]
     sources = [
       "media/pepper_cdm_test_constants.cc",
       "media/pepper_cdm_test_constants.h",
     ]
   }
 }