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

ios/chrome/browser/browsing_data/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.
 
 source_set("browsing_data") {
   sources = [
     "browsing_data_change_listening.h",
     "browsing_data_counter_wrapper.cc",
     "browsing_data_counter_wrapper.h",
     "browsing_data_remover_helper.cc",
@@ skipping 34 matching lines @@
   ]
   public_deps = [
     "//components/search_engines",
   ]
   allow_circular_includes_from = [ "//ios/chrome/browser/signin" ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 }
 
 source_set("unit_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "browsing_data_removal_controller_unittest.mm",
     "cache_counter_unittest.cc",
   ]
   deps = [
     ":browsing_data",
     ":browsing_data_internal",
     "//base",
     "//base/test:test_support",
@@ skipping 27 matching lines @@
     "//ios/chrome/browser/signin",
     "//ios/chrome/browser/snapshots",
     "//ios/chrome/browser/ui:ui_internal",
     "//ios/public/provider/chrome/browser",
     "//ios/public/provider/chrome/browser/native_app_launcher",
     "//ios/web",
     "//net",
   ]
   libs = [ "WebKit.framework" ]
 }