Migrate about:flags messages to const char*

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("//rlz/features/features.gni")
 import("//third_party/protobuf/proto_library.gni")
 
@@ skipping 28 matching lines @@
     "experimental_flags.h",
     "experimental_flags.mm",
     "file_metadata_util.h",
     "file_metadata_util.mm",
     "install_time_util.h",
     "install_time_util.mm",
     "installation_notifier.h",
     "installation_notifier.mm",
     "ios_chrome_field_trials.cc",
     "ios_chrome_field_trials.h",
+    "ios_chrome_flag_descriptions.cc",
+    "ios_chrome_flag_descriptions.h",
     "ios_chrome_io_thread.h",
     "ios_chrome_io_thread.mm",
     "notification_promo.cc",
     "notification_promo.h",
     "open_url_util.h",
     "open_url_util.mm",
     "pref_names.cc",
     "pref_names.h",
     "procedural_block_types.h",
     "root_coordinator.h",
@@ skipping 162 matching lines @@
 
 source_set("browser_internal") {
   sources = [
     "callback_counter.h",
     "callback_counter.mm",
   ]
   deps = [
     "//base",
   ]
 }