Reland Update implementation of atomics with latest Chromium version but use compiler builtin atomi…

BUILD.gn

 # Copyright 2014 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/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
@@ skipping 2175 matching lines @@
   if (v8_enable_inspector_override) {
     deps += [ "src/inspector:inspector" ]
   }
 }
 
 v8_component("v8_libbase") {
   sources = [
     "src/base/adapters.h",
     "src/base/atomic-utils.h",
     "src/base/atomicops.h",
-    "src/base/atomicops_internals_arm64_gcc.h",
-    "src/base/atomicops_internals_arm_gcc.h",
     "src/base/atomicops_internals_atomicword_compat.h",
-    "src/base/atomicops_internals_mac.h",
-    "src/base/atomicops_internals_mips64_gcc.h",
-    "src/base/atomicops_internals_mips_gcc.h",
-    "src/base/atomicops_internals_s390_gcc.h",
-    "src/base/atomicops_internals_tsan.h",
-    "src/base/atomicops_internals_x86_gcc.cc",
-    "src/base/atomicops_internals_x86_gcc.h",
+    "src/base/atomicops_internals_portable.h",
     "src/base/atomicops_internals_x86_msvc.h",
     "src/base/base-export.h",
     "src/base/bits.cc",
     "src/base/bits.h",
     "src/base/build_config.h",
     "src/base/compiler-specific.h",
     "src/base/cpu.cc",
     "src/base/cpu.h",
     "src/base/debug/stack_trace.cc",
     "src/base/debug/stack_trace.h",
@@ skipping 753 matching lines @@
   ]
 
   configs = [
     ":external_config",
     ":internal_config_base",
   ]
 }
 
 v8_fuzzer("wasm_data_section_fuzzer") {
 }