[ObjC ARC] Converts ios/chrome/browser/metrics:unit_tests to ARC.Automatically generated ARCMigra…

ios/chrome/browser/metrics/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.
 
 source_set("metrics") {
   sources = [
     "field_trial_synchronizer.cc",
     "field_trial_synchronizer.h",
     "ios_chrome_metrics_service_accessor.cc",
     "ios_chrome_metrics_service_accessor.h",
@@ skipping 39 matching lines @@
     "//ios/chrome/browser/ui",
     "//ios/chrome/browser/variations",
     "//ios/chrome/browser/variations:ios_chrome_ui_string_overrider_factory",
     "//ios/chrome/common",
     "//ios/public/provider/chrome/browser",
     "//ios/web",
   ]
 }
 
 source_set("unit_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "ios_chrome_metrics_service_accessor_unittest.cc",
     "ios_chrome_stability_metrics_provider_unittest.cc",
     "mobile_session_shutdown_metrics_provider_unittest.mm",
     "previous_session_info_unittest.mm",
   ]
   deps = [
     ":metrics",
     "//base",
     "//base/test:test_support",
     "//components/metrics",
     "//components/metrics:test_support",
     "//components/prefs",
     "//components/prefs:test_support",
     "//components/version_info",
     "//ios/chrome/test:test_support",
     "//testing/gtest",
   ]
 }