[ObjC ARC] Reland of Converts ios/chrome/browser/ui:ui to ARC.

ios/chrome/browser/ui/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("//build/config/ios/rules.gni")
 
 source_set("ui") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "UIView+SizeClassSupport.h",
     "UIView+SizeClassSupport.mm",
     "animation_util.h",
     "animation_util.mm",
     "background_generator.h",
     "background_generator.mm",
     "browser_otr_state.h",
     "browser_otr_state.mm",
     "favicon_view.h",
@@ skipping 130 matching lines @@
     "//components/resources/terms/terms_tr.html",
     "//components/resources/terms/terms_uk.html",
     "//components/resources/terms/terms_vi.html",
     "//components/resources/terms/terms_zh-CN.html",
     "//components/resources/terms/terms_zh-TW.html",
   ]
   outputs = [
     "{{bundle_resources_dir}}/{{source_file_part}}",
   ]
 }