[ObjC ARC] Converts ios/public/provider/chrome/browser:test_support to ARC.

ios/public/provider/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("//ios/public/provider/chrome/browser/build_config.gni")
 
 source_set("browser") {
   sources = [
     "chrome_browser_provider.h",
     "chrome_browser_provider.mm",
     "geolocation_updater_provider.h",
     "geolocation_updater_provider.mm",
   ]
   deps = [
     "//base",
     "//components/metrics",
   ]
   libs = [ "CoreLocation.framework" ]
 }
 
 source_set("test_support") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "test_chrome_browser_provider.h",
     "test_chrome_browser_provider.mm",
     "test_chrome_provider_initializer.h",
     "test_chrome_provider_initializer.mm",
   ]
   deps = [
     ":browser",
     "//base",
     "//ios/public/provider/chrome/browser/distribution:test_support",
     "//ios/public/provider/chrome/browser/images:test_support",
     "//ios/public/provider/chrome/browser/native_app_launcher:test_support",
     "//ios/public/provider/chrome/browser/omaha:test_support",
     "//ios/public/provider/chrome/browser/signin:test_support",
     "//ios/public/provider/chrome/browser/spotlight:test_support",
     "//ios/public/provider/chrome/browser/ui",
     "//ios/public/provider/chrome/browser/ui:test_support",
     "//ios/public/provider/chrome/browser/user_feedback:test_support",
     "//ios/public/provider/chrome/browser/voice",
     "//ios/public/provider/chrome/browser/voice:test_support",
     "//testing/gtest",
   ]
 }