Use SingleThreadedTaskQueue in DirectTransport

webrtc/test/single_threaded_task_queue.h

Index: webrtc/test/single_threaded_task_queue.h
diff --git a/webrtc/test/single_threaded_task_queue.h b/webrtc/test/single_threaded_task_queue.h
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+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef WEBRTC_TEST_SINGLE_THREADED_TASK_QUEUE_H_
+#define WEBRTC_TEST_SINGLE_THREADED_TASK_QUEUE_H_
+
+#include <functional>
+#include <list>
+#include <utility>
+
+#include "webrtc/rtc_base/criticalsection.h"
+#include "webrtc/rtc_base/event.h"
+#include "webrtc/rtc_base/optional.h"
+#include "webrtc/rtc_base/platform_thread.h"
+#include "webrtc/rtc_base/thread_checker.h"
+
+namespace webrtc {
+namespace test {
+
+// TODO(eladalon): !!! Discuss with reviewers - do we want a small unit-test
+// for this class, which is itself only used for unit-tests?
+
+// This class gives capabilities similar to rtc::TaskQueue, but insures
+// everything happens on the same thread. This is intended to make the
+// threading model of unit-tests (specifically end-to-end tests) more closely
+// resemble that of real WebRTC, thereby allowing us to replace some critical
+// sections by thread-checkers.
+// This task is NOT tuned for performance, but rather for simplicity.
+class SingleThreadedTaskQueue {
+ public:
+  using Task = std::function<void()>;
+
+  // TODO(eladalon): !!! Is there a way to make this opaque?
+  using TaskIdentifier = size_t;
+
+  explicit SingleThreadedTaskQueue(const char* name);
+  ~SingleThreadedTaskQueue();
+
+  // Sends one task to the task-queue, and returns a handle by which the
+  // task can be cancelled.
+  TaskIdentifier PostTask(Task task);
+
+  // Send one task to the queue. The function does not return until the task
+  // has finished executing. No support for canceling the task.
+  void SendTask(Task task);
+
+  // Given an identifier to the task, attempts to eject it from the queue.
+  // Returns true if the task was found and cancelled. Failure possible
+  // only for invalid task IDs, or for tasks which have already been executed.
+  bool CancelTask(TaskIdentifier task_id);
+
+ private:
+  static void Run(void* obj);
+
+  void RunLoop();
+
+  rtc::CriticalSection cs_;
+  std::list<std::pair<TaskIdentifier, Task>> tasks_ GUARDED_BY(cs_);
+  rtc::ThreadChecker owner_thread_checker_;
+  rtc::PlatformThread thread_;
+  bool running_ GUARDED_BY(cs_);
+
+  TaskIdentifier next_identifier_;
+
+  // By only Set()-ing when going from 0 pending tasks to 1 (or stopping), and
+  // only Wait()-ing when going from 1 pending tasks to 0, we ensure we never
+  // handle two calls to Set() with one call to Wait().
+  rtc::Event event_;
+};
+
+}  // namespace test
+}  // namespace webrtc
+
+#endif  // WEBRTC_TEST_SINGLE_THREADED_TASK_QUEUE_H_