Use NullSocketServer instead of PhysicalSocketServer in SignalThread

webrtc/base/signalthread.h

Index: webrtc/base/signalthread.h
diff --git a/webrtc/base/signalthread.h b/webrtc/base/signalthread.h
index ec250c6aad3063126f15de120786e9b90475b255..10d727c5b04ca3b7fad99e78506fe055dd5fd289 100644
--- a/webrtc/base/signalthread.h
+++ b/webrtc/base/signalthread.h
@@ -14,6 +14,7 @@
 #include <string>
 
 #include "webrtc/base/constructormagic.h"
+#include "webrtc/base/nullsocketserver.h"
 #include "webrtc/base/sigslot.h"
 #include "webrtc/base/thread.h"
 
@@ -40,7 +41,7 @@ class SignalThread
     : public sigslot::has_slots<>,
       protected MessageHandler {
  public:
-  SignalThread();
+  explicit SignalThread(bool use_socket_server = true);
 
   // Context: Main Thread.  Call before Start to change the worker's name.
   bool SetName(const std::string& name, const void* obj);
@@ -102,7 +103,11 @@ class SignalThread
 
   class Worker : public Thread {
    public:
-    explicit Worker(SignalThread* parent) : parent_(parent) {}
+    explicit Worker(SignalThread* parent, bool use_socket_server)
+        : Thread(use_socket_server
+                     ? SocketServer::CreateDefault()
+                     : std::unique_ptr<SocketServer>(new NullSocketServer())),
+          parent_(parent) {}
     ~Worker() override;
     void Run() override;