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

ios/chrome/browser/ui/side_swipe/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.
 
 bundle_data("resources") {
   sources = [
     "resources/side_swipe_navigation_back.png",
     "resources/side_swipe_navigation_back@2x.png",
     "resources/side_swipe_navigation_back@3x.png",
     "resources/side_swipe_navigation_content_shadow.png",
     "resources/side_swipe_navigation_content_shadow@2x.png",
     "resources/side_swipe_navigation_content_shadow@3x.png",
   ]
   outputs = [
     "{{bundle_resources_dir}}/{{source_file_part}}",
   ]
 }
 
 source_set("side_swipe") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "card_side_swipe_view.h",
     "card_side_swipe_view.mm",
     "history_side_swipe_provider.h",
     "history_side_swipe_provider.mm",
     "side_swipe_controller.h",
     "side_swipe_controller.mm",
     "side_swipe_navigation_view.h",
     "side_swipe_navigation_view.mm",
     "side_swipe_util.h",
@@ skipping 31 matching lines @@
   deps = [
     ":side_swipe",
     "//base",
     "//ios/chrome/browser/browser_state:test_support",
     "//ios/chrome/browser/ui/toolbar",
     "//ios/web:test_support",
     "//testing/gtest",
     "//third_party/ocmock",
   ]
 }