[ObjC ARC] Converts ios/web/public/test/fakes:fakes to ARC.

ios/web/public/test/fakes/BUILD.gn

 # Copyright 2017 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("fakes") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
 
   deps = [
     "//base",
     "//ios/web:web",
     "//ios/web/test:test_constants",
     "//mojo/common:common_custom_types",
     "//net:test_support",
     "//testing/gtest",
     "//ui/base",
@@ skipping 21 matching lines @@
     "test_web_state_delegate.h",
     "test_web_state_delegate.mm",
     "test_web_state_observer.h",
     "test_web_state_observer.mm",
     "test_web_state_observer_util.h",
     "test_web_state_observer_util.mm",
     "test_web_view_content_view.h",
     "test_web_view_content_view.mm",
   ]
 }