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

ios/chrome/browser/chrome_paths.mm

 // Copyright 2015 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.
 
 #include "ios/chrome/browser/chrome_paths.h"
 
 #include "base/base_paths.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/threading/thread_restrictions.h"
 #include "components/gcm_driver/gcm_driver_constants.h"
 #include "ios/chrome/browser/chrome_paths_internal.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace ios {
 namespace {
 
 #if defined(GOOGLE_CHROME_BUILD)
 const base::FilePath::CharType kProductDirName[] =
     FILE_PATH_LITERAL("Google/Chrome");
 #else
 const base::FilePath::CharType kProductDirName[] =
     FILE_PATH_LITERAL("Chromium");
 #endif
@@ skipping 85 matching lines @@
   base::FilePath cache_dir;
   if (!PathService::Get(base::DIR_CACHE, &cache_dir))
     return;
   if (!app_data_dir.AppendRelativePath(browser_state_dir, &cache_dir))
     return;
 
   *result = cache_dir;
 }
 
 }  // namespace ios