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

ios/chrome/browser/ui/BUILD.gn

 # Copyright 2016 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/ios/rules.gni")
 
 source_set("ui") {
   sources = [
     "UIView+SizeClassSupport.h",
     "UIView+SizeClassSupport.mm",
@@ skipping 325 matching lines @@
     "browser_view_controller_dependency_factory.mm",
   ]
   deps = [
     ":resources",
     ":ui",
     "//base",
     "//base:i18n",
     "//components/bookmarks/browser",
     "//components/image_fetcher/ios",
     "//components/infobars/core",
+    "//components/payments/core",
     "//components/prefs",
     "//components/reading_list/core",
     "//components/search_engines",
     "//components/sessions",
     "//components/strings",
     "//components/toolbar",
     "//components/url_formatter",
     "//ios/chrome/app:tests_hook",
     "//ios/chrome/app/strings",
     "//ios/chrome/browser",
@@ skipping 199 matching lines @@
     "//ios/chrome/browser/web_state_list",
     "//ios/chrome/browser/web_state_list:test_support",
     "//ios/chrome/test/base:perf_test_support",
     "//ios/web/public/test/fakes",
     "//testing/gtest",
     "//third_party/ocmock",
     "//ui/base:test_support",
   ]
   libs = [ "UIKit.framework" ]
 }