[ObjC ARC] Converts ios/chrome/browser/ui/keyboard:unit_tests to ARC.Automatically generated ARCM…

ios/chrome/browser/ui/keyboard/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("keyboard") {
   sources = [
     "UIKeyCommand+Chrome.h",
     "UIKeyCommand+Chrome.mm",
     "hardware_keyboard_watcher.h",
     "hardware_keyboard_watcher.mm",
   ]
   deps = [
     "//base",
     "//ios/chrome/browser/ui/commands",
   ]
 }
 
 source_set("unit_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "UIKeyCommand+ChromeTest.mm",
     "hardware_keyboard_watcher_unittest.mm",
   ]
   deps = [
     ":keyboard",
     "//base",
     "//base/test:test_support",
     "//ios/chrome/browser/ui/commands",
     "//testing/gtest",
     "//third_party/ocmock",
   ]
 }