[ObjC ARC] Converts ios/web:earl_grey_test_support 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 355 matching lines @@
     "//ios/web/public/test/fakes",
     "//ios/web/public/test/http_server",
   ]
 
   sources = [
     "public/test/http_server.h",
   ]
 }
 
 source_set("earl_grey_test_support") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
 
   deps = [
     ":web",
     "//base",
     "//base/test:test_support",
     "//ios/testing:ios_test_support",
     "//ios/testing/earl_grey:earl_grey_support",
     "//ios/third_party/earl_grey",
     "//ios/web/public/test",
@@ skipping 259 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",
   ]
 }