[ObjC ARC] Converts ios/chrome/browser/web:web to ARC.

ios/chrome/browser/web/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("//ios/web/js_compile.gni")
 
 source_set("web") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "dom_altering_lock.h",
     "dom_altering_lock.mm",
     "network_activity_indicator_tab_helper.h",
     "network_activity_indicator_tab_helper.mm",
     "resubmit_data_controller.h",
     "resubmit_data_controller.mm",
   ]
   deps = [
     "//base",
@@ skipping 129 matching lines @@
   outputs = [
     "{{bundle_resources_dir}}/{{source_file_part}}",
   ]
 }
 
 js_compile_unchecked("injected_js") {
   sources = [
     "resources/print.js",
   ]
 }