Add TimeController to api/test/ and add a CreateTimeController API.

Creates an abstraction for an "alarm clock" which can schedule
time-controller callbacks and exposes a time controller driven by
an external alarm.

Bug: webrtc:9719
Change-Id: I08c2aa9dba25603043bfba48f55c925716a55bae
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/158969
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Bjorn Mellem <mellem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29879}
diff --git a/api/test/time_controller.h b/api/test/time_controller.h
new file mode 100644
index 0000000..4723716
--- /dev/null
+++ b/api/test/time_controller.h
@@ -0,0 +1,75 @@
+/*
+ *  Copyright 2019 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 API_TEST_TIME_CONTROLLER_H_
+#define API_TEST_TIME_CONTROLLER_H_
+
+#include <functional>
+#include <memory>
+
+#include "api/task_queue/task_queue_factory.h"
+#include "api/units/time_delta.h"
+#include "api/units/timestamp.h"
+#include "modules/utility/include/process_thread.h"
+#include "rtc_base/synchronization/yield_policy.h"
+#include "system_wrappers/include/clock.h"
+
+namespace webrtc {
+
+// Interface for controlling time progress. This allows us to execute test code
+// in either real time or simulated time by using different implementation of
+// this interface.
+class TimeController {
+ public:
+  virtual ~TimeController() = default;
+  // Provides a clock instance that follows implementation defined time
+  // progress.
+  virtual Clock* GetClock() = 0;
+  // The returned factory will created task queues that runs in implementation
+  // defined time domain.
+  virtual TaskQueueFactory* GetTaskQueueFactory() = 0;
+  // Creates a process thread.
+  virtual std::unique_ptr<ProcessThread> CreateProcessThread(
+      const char* thread_name) = 0;
+  // Allow task queues and process threads created by this instance to execute
+  // for the given |duration|.
+  virtual void Sleep(TimeDelta duration) = 0;
+  // Execute closure in an implementation defined scope where rtc::Event::Wait
+  // might yield to execute other tasks. This allows doing blocking waits on
+  // tasks on other task queues froma a task queue without deadlocking.
+  virtual void InvokeWithControlledYield(std::function<void()> closure) = 0;
+  // Returns a YieldInterface which can be installed as a ScopedYieldPolicy.
+  virtual rtc::YieldInterface* YieldInterface() = 0;
+};
+
+// Interface for telling time, scheduling an event to fire at a particular time,
+// and waiting for time to pass.
+class ControlledAlarmClock {
+ public:
+  virtual ~ControlledAlarmClock() = default;
+
+  // Gets a clock that tells the alarm clock's notion of time.
+  virtual Clock* GetClock() = 0;
+
+  // Schedules the alarm to fire at |deadline|.
+  // An alarm clock only supports one deadline. Calls to |ScheduleAlarmAt| with
+  // an earlier deadline will reset the alarm to fire earlier.Calls to
+  // |ScheduleAlarmAt| with a later deadline are ignored. Returns true if the
+  // deadline changed, false otherwise.
+  virtual bool ScheduleAlarmAt(Timestamp deadline) = 0;
+
+  // Sets the callback that should be run when the alarm fires.
+  virtual void SetCallback(std::function<void()> callback) = 0;
+
+  // Waits for |duration| to pass, according to the alarm clock.
+  virtual void Sleep(TimeDelta duration) = 0;
+};
+
+}  // namespace webrtc
+#endif  // API_TEST_TIME_CONTROLLER_H_