Adds clearer function to create rtc::Thread without Physical SocketServer

webrtc/base/messagequeue.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 157 matching lines @@
 
 class MessageQueue {
  public:
   static const int kForever = -1;
 
   // Create a new MessageQueue and optionally assign it to the passed
   // SocketServer. Subclasses that override Clear should pass false for
   // init_queue and call DoInit() from their constructor to prevent races
   // with the MessageQueueManager using the object while the vtable is still
   // being created.
-  explicit MessageQueue(SocketServer* ss = NULL,
-                        bool init_queue = true);
+  MessageQueue(SocketServer* ss, bool init_queue);
+  MessageQueue(std::unique_ptr<SocketServer> ss, bool init_queue);
 
   // NOTE: SUBCLASSES OF MessageQueue THAT OVERRIDE Clear MUST CALL
   // DoDestroy() IN THEIR DESTRUCTORS! This is required to avoid a data race
   // between the destructor modifying the vtable, and the MessageQueueManager
   // calling Clear on the object from a different thread.
   virtual ~MessageQueue();
 
   SocketServer* socketserver();
   void set_socketserver(SocketServer* ss);
 
@@ skipping 79 matching lines @@
   bool fPeekKeep_;
   Message msgPeek_;
   MessageList msgq_ GUARDED_BY(crit_);
   PriorityQueue dmsgq_ GUARDED_BY(crit_);
   uint32_t dmsgq_next_num_ GUARDED_BY(crit_);
   CriticalSection crit_;
   bool fInitialized_;
   bool fDestroyed_;
 
  private:
-  // The SocketServer is not owned by MessageQueue.
+  // The SocketServer might not be owned by MessageQueue.
   SocketServer* ss_ GUARDED_BY(ss_lock_);
-  // If a server isn't supplied in the constructor, use this one.
-  std::unique_ptr<SocketServer> default_ss_;
+  // Used if SocketServer ownership lies with |this|.
+  std::unique_ptr<SocketServer> own_ss_;
   SharedExclusiveLock ss_lock_;
 
-  RTC_DISALLOW_COPY_AND_ASSIGN(MessageQueue);
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(MessageQueue);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_MESSAGEQUEUE_H_