[ObjC ARC] Converts ios/chrome/app/application_delegate:test_support to ARC.

ios/chrome/app/application_delegate/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("application_delegate") {
   sources = [
     "memory_warning_helper.h",
     "memory_warning_helper.mm",
   ]
   deps = [
@@ skipping 114 matching lines @@
     "//ui/base",
     "//url",
   ]
   libs = [
     "CoreSpotlight.framework",
     "UIKit.framework",
   ]
 }
 
 source_set("test_support") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "app_state_testing.h",
     "fake_startup_information.h",
     "fake_startup_information.mm",
     "metrics_mediator_testing.h",
     "mock_tab_opener.h",
     "mock_tab_opener.mm",
   ]
   deps = [
     ":application_delegate_internal",
     "//base",
     "//base/test:test_support",
     "//ios/chrome/app:app_internal",
     "//ios/chrome/browser",
     "//net",
     "//ui/base",
     "//url",
   ]
   libs = [ "UIKit.framework" ]
 }