[ObjC ARC] Converts ios/chrome/browser/ui/omnibox:omnibox_internal to ARC.

ios/chrome/browser/ui/omnibox/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("omnibox") {
   sources = [
     "omnibox_util.cc",
     "omnibox_util.h",
     "web_omnibox_edit_controller.cc",
     "web_omnibox_edit_controller.h",
@@ skipping 14 matching lines @@
     "resources/omnibox_transparent_background.png",
     "resources/omnibox_transparent_background@2x.png",
     "resources/omnibox_transparent_background@3x.png",
   ]
   outputs = [
     "{{bundle_resources_dir}}/{{source_file_part}}",
   ]
 }
 
 source_set("omnibox_internal") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "chrome_omnibox_client_ios.h",
     "chrome_omnibox_client_ios.mm",
     "location_bar_view_ios.h",
     "location_bar_view_ios.mm",
     "omnibox_popup_material_row.h",
     "omnibox_popup_material_row.mm",
     "omnibox_popup_material_view_controller.h",
     "omnibox_popup_material_view_controller.mm",
     "omnibox_popup_positioner.h",
@@ skipping 86 matching lines @@
   visibility = [ ":unit_tests" ]
   testonly = true
   sources = [
     "//ios/chrome/test/data/omnibox/selected_ranges.txt",
   ]
   outputs = [
     "{{bundle_resources_dir}}/" +
         "ios/chrome/test/data/omnibox/{{source_file_part}}",
   ]
 }