Delete unused use_socket_server argument.

Bug: webrtc:7723
Change-Id: Ie048f59ed482d509742170cca6c9c1887c58dafd
Reviewed-on: https://webrtc-review.googlesource.com/39507
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21649}

rtc_base/nethelpers.cc

@@ -84,7 +84,7 @@ int ResolveHostname(const std::string& hostname, int family,
 
 // AsyncResolver
 AsyncResolver::AsyncResolver()
-    : SignalThread(false /* use_socket_server */), error_(-1) {}
+    : SignalThread(), error_(-1) {}
 
 AsyncResolver::~AsyncResolver() = default;
 

rtc_base/signalthread.cc

@@ -18,9 +18,9 @@ namespace rtc {
 // SignalThread
 ///////////////////////////////////////////////////////////////////////////////
 
-SignalThread::SignalThread(bool use_socket_server)
+SignalThread::SignalThread()
     : main_(Thread::Current()),
-      worker_(this, use_socket_server),
+      worker_(this),
       state_(kInit),
       refcount_(1) {
   main_->SignalQueueDestroyed.connect(this,

rtc_base/signalthread.h

@@ -42,7 +42,7 @@ class SignalThread
     : public sigslot::has_slots<>,
       protected MessageHandler {
  public:
-  explicit SignalThread(bool use_socket_server = true);
+  SignalThread();
 
   // Context: Main Thread.  Call before Start to change the worker's name.
   bool SetName(const std::string& name, const void* obj);
@@ -104,10 +104,8 @@ class SignalThread
 
   class Worker : public Thread {
    public:
-    explicit Worker(SignalThread* parent, bool use_socket_server)
-        : Thread(use_socket_server
-                     ? SocketServer::CreateDefault()
-                     : std::unique_ptr<SocketServer>(new NullSocketServer())),
+    explicit Worker(SignalThread* parent)
+        : Thread(std::unique_ptr<SocketServer>(new NullSocketServer())),
           parent_(parent) {}
     ~Worker() override;
     void Run() override;