[Payments] Add an entry for Payment Request to chrome://flags on iOS

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 76 matching lines @@
     "//components/flags_ui",
     "//components/flags_ui:switches",
     "//components/handoff",
     "//components/keyed_service/core",
     "//components/keyed_service/ios",
     "//components/metrics",
     "//components/metrics_services_manager",
     "//components/net_log",
     "//components/ntp_tiles",
     "//components/password_manager/core/common:common",
+    "//components/payments/core",
     "//components/pref_registry",
     "//components/prefs",
     "//components/proxy_config",
     "//components/proxy_config/ios",
     "//components/reading_list/ios",
     "//components/search_engines",
     "//components/security_state/core",
     "//components/signin/core/browser",
     "//components/ssl_config",
     "//components/strings",
@@ skipping 137 matching lines @@
 source_set("browser_internal") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "callback_counter.h",
     "callback_counter.mm",
   ]
   deps = [
     "//base",
   ]
 }