Delete SignalThread class.

webrtc/base/nethelpers.h

Index: webrtc/base/nethelpers.h
diff --git a/webrtc/base/nethelpers.h b/webrtc/base/nethelpers.h
index b0727f861b6a2910b225b839447e21d02911bc74..878a04ab5b36b2cc37c21369e99c93a3c83084fa 100644
--- a/webrtc/base/nethelpers.h
+++ b/webrtc/base/nethelpers.h
@@ -19,19 +19,23 @@
 #endif
 
 #include <list>
+#include <memory>
 
 #include "webrtc/base/asyncresolverinterface.h"
-#include "webrtc/base/signalthread.h"
 #include "webrtc/base/sigslot.h"
 #include "webrtc/base/socketaddress.h"
+#include "webrtc/base/thread_checker.h"
 
 namespace rtc {
 
-class AsyncResolverTest;
+class Thread;
+class TaskQueue;
 
-// AsyncResolver will perform async DNS resolution, signaling the result on
-// the SignalDone from AsyncResolverInterface when the operation completes.
-class AsyncResolver : public SignalThread, public AsyncResolverInterface {
+// AsyncResolver will perform async DNS resolution, signaling the result on the
+// SignalDone from AsyncResolverInterface when the operation completes.
+// SignalDone is fired on the same thread on which the AsyncResolver was
+// constructed.
+class AsyncResolver : public AsyncResolverInterface {
  public:
   AsyncResolver();
   ~AsyncResolver() override;
@@ -42,16 +46,20 @@ class AsyncResolver : public SignalThread, public AsyncResolverInterface {
   void Destroy(bool wait) override;
 
   const std::vector<IPAddress>& addresses() const { return addresses_; }
-  void set_error(int error) { error_ = error; }
-
- protected:
-  void DoWork() override;
-  void OnWorkDone() override;
 
  private:
+  void ResolveDone(int error, std::vector<IPAddress> addresses);
+
+  enum class State { NONE, PENDING, DESTROYED };
+
+  State state_ ACCESS_ON(construction_thread_);
+
+  rtc::Thread* const construction_thread_;
+  // Queue used only for a single task.
+  std::unique_ptr<TaskQueue> resolver_queue_;
   SocketAddress addr_;
   std::vector<IPAddress> addresses_;
-  int error_;
+  int error_ = -1;
 };
 
 // rtc namespaced wrappers for inet_ntop and inet_pton so we can avoid