Introduce a RunLoop class that supports the TaskQueue interface
on the current thread.

This simplifies writing async tests that use TaskQueue and doesn't
require spinning up a new thread for simple things. The implementation
is currently based on rtc::Thread, which could also be useful in
some circumstances while migrating code over to TQ.

Remove PressEnterToContinue from the test_common files since
it's very specific and only used from one file.

Bug: none
Change-Id: I8b2c6c40809271a109ec17cf7e1120847645d58a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/174260
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31160}

test/run_loop.h

diff --git a/test/run_loop.h b/test/run_loop.h
index 414e72c..f350b2c 100644
--- a/test/run_loop.h
+++ b/test/run_loop.h
@@ -10,13 +10,69 @@
 #ifndef TEST_RUN_LOOP_H_
 #define TEST_RUN_LOOP_H_
 
-#include "api/task_queue/task_queue_base.h"
+#include "rtc_base/task_utils/to_queued_task.h"
+#include "rtc_base/thread.h"
 
 namespace webrtc {
 namespace test {
 
-// Blocks until the user presses enter.
-void PressEnterToContinue(TaskQueueBase* task_queue);
+// This utility class allows you to run a TaskQueue supported interface on the
+// main test thread, call Run() while doing things asynchonously and break
+// the loop (from the same thread) from a callback by calling Quit().
+class RunLoop {
+ public:
+  RunLoop();
+  ~RunLoop();
+
+  TaskQueueBase* task_queue();
+
+  void Run();
+  void Quit();
+
+  void Flush();
+
+  // Convenience methods since TaskQueueBase doesn't support this sort of magic.
+  template <typename Closure>
+  void PostTask(Closure&& task) {
+    task_queue()->PostTask(ToQueuedTask(std::forward<Closure>(task)));
+  }
+
+  template <typename Closure>
+  void PostDelayedTask(Closure&& task, uint32_t milliseconds) {
+    task_queue()->PostDelayedTask(ToQueuedTask(std::forward<Closure>(task)),
+                                  milliseconds);
+  }
+
+ private:
+  class FakeSocketServer : public rtc::SocketServer {
+   public:
+    FakeSocketServer();
+    ~FakeSocketServer();
+
+    void FailNextWait();
+
+   private:
+    bool Wait(int cms, bool process_io) override;
+    void WakeUp() override;
+
+    rtc::Socket* CreateSocket(int family, int type) override;
+    rtc::AsyncSocket* CreateAsyncSocket(int family, int type) override;
+
+   private:
+    bool fail_next_wait_ = false;
+  };
+
+  class WorkerThread : public rtc::Thread {
+   public:
+    explicit WorkerThread(rtc::SocketServer* ss);
+
+   private:
+    CurrentTaskQueueSetter tq_setter_;
+  };
+
+  FakeSocketServer socket_server_;
+  WorkerThread worker_thread_{&socket_server_};
+};
 
 }  // namespace test
 }  // namespace webrtc