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

ios/web/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("//ios/build/config.gni")
 import("//ios/web/js_compile.gni")
 import("//testing/test.gni")
 import("//tools/grit/grit_rule.gni")
 
 group("all_tests") {
@@ skipping 242 matching lines @@
     "webui/web_ui_ios_impl.h",
     "webui/web_ui_ios_impl.mm",
   ]
 
   libs = [ "WebKit.framework" ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 }
 
 source_set("web") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   deps = [
     ":core",
     ":js_resources",
     ":reload_type",
     ":resources",
     ":user_agent",
     "//base",
     "//components/url_formatter",
     "//ios/net",
     "//ios/third_party/blink:html_tokenizer",
@@ skipping 372 matching lines @@
     "ios_web_resources.pak",
   ]
   grit_flags = [
     "-E",
     "root_gen_dir=" + rebase_path(root_gen_dir, root_build_dir),
   ]
   deps = [
     "//mojo/public/js:bindings",
   ]
 }