Add Darwin thread.h implementation.

webrtc/base/thread.h

 /*
  *  Copyright 2004 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.
  */
 
@@ skipping 220 matching lines @@
   void SafeWrapCurrent();
 
   // Blocks the calling thread until this thread has terminated.
   void Join();
 
   static void AssertBlockingIsAllowedOnCurrentThread();
 
   friend class ScopedDisallowBlockingCalls;
 
  private:
+  struct ThreadInit {
+    Thread* thread;
+    Runnable* runnable;
+  };
+
 #if defined(WEBRTC_WIN)
   static DWORD WINAPI PreRun(LPVOID context);
 #else
   static void *PreRun(void *pv);
 #endif
 
   // ThreadManager calls this instead WrapCurrent() because
   // ThreadManager::Instance() cannot be used while ThreadManager is
   // being created.
   // The method tries to get synchronization rights of the thread on Windows if
@@ skipping 78 matching lines @@
 
  private:
   SocketServer* old_ss_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(SocketServerScope);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_THREAD_H_