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

ios/chrome/app/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/config/ios/rules.gni")
 import("//build/config/mac/base_rules.gni")
 import("//build/mac/tweak_info_plist.gni")
 import("//ios/build/chrome_build.gni")
 import("//ios/public/provider/chrome/browser/build_config.gni")
 
@@ skipping 95 matching lines @@
   format = "xml1"
   plist_templates = [ "resources/Chrome.entitlements" ]
   if (ios_chrome_entitlements_additions != []) {
     plist_templates += ios_chrome_entitlements_additions
   }
   substitutions = [ "IOS_BUNDLE_ID_PREFIX=$ios_app_bundle_id_prefix" ]
   output_name = "$target_gen_dir/$chromium_short_name.entitlements"
 }
 
 source_set("app_internal") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "application_mode.h",
     "chrome_app_startup_parameters.h",
     "chrome_app_startup_parameters.mm",
     "chrome_overlay_window.h",
     "chrome_overlay_window.mm",
     "main_application_delegate.h",
     "main_application_delegate.mm",
     "main_application_delegate_testing.h",
     "main_controller.h",
@@ skipping 229 matching lines @@
       ]
       sources = [
         "$root_out_dir/share_extension.appex",
       ]
       outputs = [
         "{{bundle_plugins_dir}}/{{source_file_part}}",
       ]
     }
   }
 }