Convert //ios/chrome/browser:about_flags to use buildflag_header.

ios/chrome/browser/BUILD.gn

 # 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.
 
+import("//build/buildflag_header.gni")
 import("//build/config/features.gni")
 import("//build/config/ios/rules.gni")
 import("//third_party/protobuf/proto_library.gni")
 
 declare_args() {
   google_test_gaia_client_id = ""
   google_test_gaia_client_secret = ""
   google_staging_api_url = ""
   google_staging_lso_url = ""
   google_test_api_url = ""
   google_test_lso_url = ""
   google_test_oauth_client_id = ""
   google_test_oauth_client_secret = ""
   google_test_oauth_url = ""
   google_test_sync_url = ""
 }
 
 source_set("browser") {
   sources = [
+    "about_flags.h",
+    "about_flags.mm",
     "app_startup_parameters.h",
     "app_startup_parameters.mm",
     "application_context.cc",
     "application_context.h",
     "arch_util.cc",
     "arch_util.h",
     "browser_about_rewriter.cc",
     "browser_about_rewriter.h",
     "chrome_constants.cc",
     "chrome_constants.h",
@@ skipping 33 matching lines @@
     "root_coordinator.mm",
     "storekit_launcher.h",
     "tab_parenting_global_observer.cc",
     "tab_parenting_global_observer.h",
     "web_data_service_factory.cc",
     "web_data_service_factory.h",
     "xcallback_parameters.h",
     "xcallback_parameters.mm",
   ]
   deps = [
+    ":google_api_keys_header",
     ":settings_resources",
     "//base",
     "//components/autofill/core/browser",
     "//components/autofill/core/common",
+    "//components/dom_distiller/core",
+    "//components/flags_ui",
+    "//components/flags_ui:switches",
     "//components/gcm_driver",
     "//components/handoff",
     "//components/keyed_service/core",
     "//components/keyed_service/ios",
     "//components/metrics",
     "//components/metrics_services_manager",
     "//components/net_log",
     "//components/network_session_configurator",
     "//components/ntp_tiles",
     "//components/pref_registry",
     "//components/prefs",
     "//components/proxy_config",
     "//components/reading_list/core",
     "//components/reading_list/ios",
     "//components/search_engines",
     "//components/signin/core/browser",
     "//components/ssl_config",
+    "//components/strings",
+    "//components/sync",
     "//components/translate/core/browser",
     "//components/url_formatter",
     "//components/variations",
     "//components/variations/service",
     "//components/version_info",
     "//components/webdata_services",
+    "//google_apis",
+    "//ios/chrome/app/strings",
     "//ios/chrome/browser/browser_state",
     "//ios/chrome/browser/sync/glue",
     "//ios/chrome/common",
     "//ios/net",
     "//ios/public/provider/chrome/browser",
     "//ios/public/provider/chrome/browser/voice",
     "//ios/web",
     "//ios/web:user_agent",
     "//net",
     "//url",
   ]
   allow_circular_includes_from = [
     "//ios/chrome/browser/sync/glue",
     "//ios/chrome/browser/browser_state",
   ]
   libs = [ "UIKit.framework" ]
 }
 
 source_set("browser_impl") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "application_context_impl.cc",
     "application_context_impl.h",
     "ios_chrome_main_parts.h",
     "ios_chrome_main_parts.mm",
   ]
   deps = [
-    ":about_flags",
     ":browser",
     "//base",
     "//components/component_updater",
     "//components/content_settings/core/browser",
     "//components/content_settings/core/common",
     "//components/flags_ui",
     "//components/gcm_driver",
     "//components/history/core/browser",
     "//components/keyed_service/core",
     "//components/language_usage_metrics",
@@ skipping 31 matching lines @@
     "//ios/web/public/app",
     "//net",
     "//ui/base",
   ]
 
   if (enable_rlz) {
     deps += [ "//ios/chrome/browser/rlz" ]
   }
 }
 
-# This is a separate target so that the 'defines' does not leak to the
-# other files (which would increase the compilation time when changing
-# the value).
-source_set("about_flags") {
-  configs += [ "//build/config/compiler:enable_arc" ]
-  sources = [
-    "about_flags.h",
-    "about_flags.mm",
-  ]
-
-  deps = [
-    ":browser",
-    "//base",
-    "//components/autofill/core/common",
-    "//components/dom_distiller/core",
-    "//components/flags_ui",
-    "//components/flags_ui:switches",
-    "//components/ntp_tiles",
-    "//components/reading_list/core",
-    "//components/strings",
-    "//components/sync",
-    "//components/variations",
-    "//google_apis",
-    "//ios/chrome/app/strings",
-    "//ios/web",
-    "//ios/web:user_agent",
-  ]
-
-  defines = [
+buildflag_header("google_api_keys_header") {
+  header = "google_api_keys.h"
+  flags = [
     "GOOGLE_STAGING_API_URL=\"$google_staging_api_url\"",
     "GOOGLE_STAGING_LSO_URL=\"$google_staging_lso_url\"",
     "GOOGLE_TEST_API_URL=\"$google_test_api_url\"",
     "GOOGLE_TEST_LSO_URL=\"$google_test_lso_url\"",
     "GOOGLE_TEST_OAUTH_CLIENT_ID=\"$google_test_oauth_client_id\"",
     "GOOGLE_TEST_OAUTH_CLIENT_SECRET=\"$google_test_oauth_client_secret\"",
     "GOOGLE_TEST_OAUTH_URL=\"$google_test_oauth_url\"",
     "GOOGLE_TEST_SYNC_URL=\"$google_test_sync_url\"",
   ]
 }
@@ skipping 27 matching lines @@
     "//components/proxy_config",
     "//components/ssl_config",
     "//components/variations",
     "//ios/web:test_support",
     "//net",
     "//net:test_support",
     "//testing/gtest",
     "//url",
   ]
 }