Revert of Remove old/unused atomicops code

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.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
@@ skipping 122 matching lines @@
     "android/trace_event_binding.cc",
     "android/trace_event_binding.h",
     "async_socket_io_handler.h",
     "async_socket_io_handler_posix.cc",
     "async_socket_io_handler_win.cc",
     "at_exit.cc",
     "at_exit.h",
     "atomic_ref_count.h",
     "atomic_sequence_num.h",
     "atomicops.h",
+    "atomicops_internals_gcc.h",
     "atomicops_internals_mac.h",
     "atomicops_internals_portable.h",
+    "atomicops_internals_x86_gcc.cc",
+    "atomicops_internals_x86_gcc.h",
     "atomicops_internals_x86_msvc.h",
     "auto_reset.h",
     "barrier_closure.cc",
     "barrier_closure.h",
     "base64.cc",
     "base64.h",
     "base_export.h",
     "base_switches.h",
     "basictypes.h",
     "big_endian.cc",
@@ skipping 1407 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" ]
   }
 }