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

ios/chrome/browser/ui/tools_menu/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("tools_menu") {
   sources = [
     "reading_list_menu_view_item.h",
     "reading_list_menu_view_item.mm",
     "tools_menu_context.h",
     "tools_menu_context.mm",
@@ skipping 26 matching lines @@
     "//ios/third_party/material_roboto_font_loader_ios",
     "//ui/base",
   ]
   libs = [
     "QuartzCore.framework",
     "UIKit.framework",
   ]
 }
 
 source_set("unit_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "tools_menu_view_item_unittest.mm",
   ]
   deps = [
     ":tools_menu",
     "//base",
     "//testing/gtest",
   ]
 }
@@ skipping 11 matching lines @@
     "//ios/chrome/browser/ui",
     "//ios/chrome/browser/ui:ui_internal",
     "//ios/chrome/browser/ui/toolbar",
     "//ios/chrome/test/earl_grey:test_support",
     "//ios/third_party/earl_grey",
     "//ios/web:test_support",
     "//ui/base",
   ]
   libs = [ "XCTest.framework" ]
 }