[ObjC ARC] Converts ios/chrome/browser/payments:unit_tests to ARC.

ios/chrome/browser/payments/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("//ios/web/js_compile.gni")
 
 js_compile_checked("injected_js") {
   sources = [
     "resources/payment_request_manager.js",
   ]
@@ skipping 52 matching lines @@
     "//ios/chrome/browser/ui/icons",
     "//ios/third_party/material_components_ios",
     "//ios/third_party/material_roboto_font_loader_ios",
     "//ios/web",
     "//ui/base",
   ]
   libs = [ "UIKit.framework" ]
 }
 
 source_set("unit_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "payment_items_display_coordinator_unittest.mm",
     "payment_items_display_view_controller_unittest.mm",
     "payment_method_selection_coordinator_unittest.mm",
     "payment_method_selection_view_controller_unittest.mm",
     "payment_request_coordinator_unittest.mm",
     "payment_request_test_util.h",
     "payment_request_test_util.mm",
     "payment_request_unittest.mm",
@@ skipping 19 matching lines @@
     "//ios/chrome/browser/ui/collection_view/cells:test_support",
     "//ios/chrome/test:test_support",
     "//ios/testing:ocmock_support",
     "//ios/third_party/material_components_ios",
     "//ios/web",
     "//ios/web:test_support",
     "//testing/gtest",
     "//third_party/ocmock",
   ]
 }