Add Darwin thread.h implementation.

webrtc/base/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/crypto.gni")
 import("//build/config/ui.gni")
@@ skipping 526 matching lines @@
     ]
 
     libs += [
       "log",
       "GLESv2",
     ]
   }
 
   if (is_ios || is_mac) {
     sources += [
-      "maccocoathreadhelper.h",
-      "maccocoathreadhelper.mm",
       "macifaddrs_converter.cc",
-      "scoped_autorelease_pool.h",
-      "scoped_autorelease_pool.mm",
+      "thread_darwin.mm",
     ]
   }
 
   if (use_x11) {
     libs += [
       "dl",
       "rt",
       "Xext",
       "X11",
       "Xcomposite",
@@ skipping 335 matching lines @@
 
 if (is_android) {
   android_library("base_java") {
     java_files = [
       "java/src/org/webrtc/Logging.java",
       "java/src/org/webrtc/Size.java",
       "java/src/org/webrtc/ThreadUtils.java",
     ]
   }
 }