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

webrtc/base/thread.h

Index: webrtc/base/thread.h
diff --git a/webrtc/base/thread.h b/webrtc/base/thread.h
index df5a686952f4efe49ea3873a844d245016b8c218..8024d2c082a34e01a01f600b72e1d01b6f792ac7 100644
--- a/webrtc/base/thread.h
+++ b/webrtc/base/thread.h
@@ -99,7 +99,10 @@ class Thread : public MessageQueue {
   // DoInit() from their constructor to prevent races with the
   // MessageQueueManager already using the object while the vtable is still
   // being created.
-  explicit Thread(SocketServer* ss = nullptr, bool init_queue = true);
+  Thread();
+  explicit Thread(SocketServer* ss);
+  Thread(SocketServer* ss, bool init_queue);
+  Thread(std::unique_ptr<SocketServer> ss, bool init_queue);
 
   // NOTE: ALL SUBCLASSES OF Thread MUST CALL Stop() IN THEIR DESTRUCTORS (or
   // guarantee Stop() is explicitly called before the subclass is destroyed).
@@ -107,6 +110,8 @@ class Thread : public MessageQueue {
   // vtable, and the Thread::PreRun calling the virtual method Run().
   ~Thread() override;
 
+  static std::unique_ptr<Thread> CreateWithSocketServer();
+  static std::unique_ptr<Thread> Create();
   static Thread* Current();
 
   // Used to catch performance regressions. Use this to disallow blocking calls
@@ -291,7 +296,7 @@ class Thread : public MessageQueue {
 
 class AutoThread : public Thread {
  public:
-  explicit AutoThread(SocketServer* ss = nullptr);
+  AutoThread();
   ~AutoThread() override;
 
  private: