[ObjC ARC] Converts ios/chrome/browser/test:perf_test_support to ARC.

ios/chrome/browser/test/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/public/provider/chrome/browser/build_config.gni")
 
 source_set("perf_test_support") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "perf_test_with_bvc_ios.h",
     "perf_test_with_bvc_ios.mm",
   ]
   deps = [
     "//base",
     "//components/bookmarks/test",
     "//ios/chrome/browser/autocomplete",
     "//ios/chrome/browser/bookmarks",
     "//ios/chrome/browser/browser_state:test_support",
     "//ios/chrome/browser/search_engines",
     "//ios/chrome/browser/sessions",
     "//ios/chrome/browser/sessions:serialisation",
     "//ios/chrome/browser/tabs",
     "//ios/chrome/browser/ui:ui_internal",
     "//ios/chrome/browser/web:web_internal",
     "//ios/chrome/test:test_support",
     "//ios/chrome/test/base:perf_test_support",
     "//ios/public/provider/chrome/browser",
     "//ios/web:test_support",
 
     # Perf tests can run with any provider, but the resulting numbers will only
     # be meaningful if ChromeBrowserProviderImpl is used.
     ios_provider_target,
   ]
   libs = [ "UIKit.framework" ]
 }