base: Use compiler builtins for byte swapping

base/BUILD.gn

 # Copyright (c) 2013 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.
 
 # HOW TO WRITE CONDITIONALS IN THIS FILE
 # ======================================
 #
 # In many other places, one would write a conditional that expresses all the
 # cases when a source file is used or unused, and then either add or subtract
 # it from the sources list in that case
@@ skipping 1847 matching lines @@
     "strings/utf_offset_string_conversions_unittest.cc",
     "strings/utf_string_conversions_unittest.cc",
     "supports_user_data_unittest.cc",
     "sync_socket_unittest.cc",
     "synchronization/cancellation_flag_unittest.cc",
     "synchronization/condition_variable_unittest.cc",
     "synchronization/lock_unittest.cc",
     "synchronization/read_write_lock_unittest.cc",
     "synchronization/waitable_event_unittest.cc",
     "synchronization/waitable_event_watcher_unittest.cc",
+    "sys_byteorder_unittest.cc",
     "sys_info_unittest.cc",
     "system_monitor/system_monitor_unittest.cc",
     "task/cancelable_task_tracker_unittest.cc",
     "task_runner_util_unittest.cc",
     "task_scheduler/delayed_task_manager_unittest.cc",
     "task_scheduler/priority_queue_unittest.cc",
     "task_scheduler/scheduler_lock_unittest.cc",
     "task_scheduler/scheduler_service_thread_unittest.cc",
     "task_scheduler/scheduler_thread_pool_impl_unittest.cc",
     "task_scheduler/scheduler_worker_thread_stack_unittest.cc",
@@ skipping 513 matching lines @@
 
   # GYP: //base.gyp:base_java_unittest_support
   android_library("base_java_unittest_support") {
     deps = [
       ":base_java",
     ]
     java_files =
         [ "test/android/java/src/org/chromium/base/ContentUriTestUtils.java" ]
   }
 }