[ObjC ARC] Converts ios/chrome/browser/ui/contextual_search:test_support to ARC.

ios/chrome/browser/ui/contextual_search/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")
 
 bundle_data("resources") {
   sources = [
     "resources/expand_less.png",
     "resources/expand_less@2x.png",
@@ skipping 86 matching lines @@
     "//ios/third_party/material_roboto_font_loader_ios",
     "//ios/web",
     "//net",
     "//ui/base",
     "//url",
   ]
   libs = [ "UIKit.framework" ]
 }
 
 source_set("test_support") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "touch_to_search_permissions_mediator+testing.h",
     "touch_to_search_permissions_mediator+testing.mm",
   ]
   deps = [
     ":contextual_search",
   ]
 }
 
@@ skipping 18 matching lines @@
     "//ios/chrome/browser/sync",
     "//ios/chrome/browser/sync:test_support",
     "//ios/chrome/browser/web:test_support",
     "//ios/web",
     "//ios/web:test_support",
     "//net",
     "//testing/gtest",
     "//third_party/ocmock",
   ]
 }