[ObjC ARC] Converts ios/chrome/test/earl_grey:ios_chrome_multitasking_egtests to ARC.

ios/chrome/test/earl_grey/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/chrome/test/earl_grey/chrome_ios_eg_test.gni")
 
 group("all_tests") {
   testonly = true
   deps = [
     ":ios_chrome_device_check_egtests",
@@ skipping 59 matching lines @@
   ]
 }
 
 chrome_ios_eg_test("ios_chrome_web_egtests") {
   deps = [
     "//ios/chrome/browser/web:eg_tests",
   ]
 }
 
 chrome_ios_eg_test("ios_chrome_multitasking_egtests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "//ios/chrome/app/multitasking_test_application_delegate.h",
     "//ios/chrome/app/multitasking_test_application_delegate.mm",
   ]
 
   deps = [
     ":test_support",
     "//base",
     "//ios/chrome/app:app_internal",
     "//ios/chrome/app/application_delegate:application_delegate_internal",
@@ skipping 114 matching lines @@
 source_set("hooks") {
   configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "eg_tests_hook.mm",
   ]
   deps = [
     "//ios/chrome/app:tests_hook",
   ]
 }