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}

api/test/create_time_controller_unittest.cc

@@ -0,0 +1,76 @@
+/*
+ *  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.
+ */
+
+#include "api/test/create_time_controller.h"
+
+#include "api/test/time_controller.h"
+#include "api/units/time_delta.h"
+#include "api/units/timestamp.h"
+#include "test/gmock.h"
+#include "test/gtest.h"
+
+namespace webrtc {
+namespace {
+
+class FakeAlarm : public ControlledAlarmClock {
+ public:
+  explicit FakeAlarm(Timestamp start_time);
+
+  Clock* GetClock() override;
+  bool ScheduleAlarmAt(Timestamp deadline) override;
+  void SetCallback(std::function<void()> callback) override;
+  void Sleep(TimeDelta duration) override;
+
+ private:
+  SimulatedClock clock_;
+  Timestamp deadline_;
+  std::function<void()> callback_;
+};
+
+FakeAlarm::FakeAlarm(Timestamp start_time)
+    : clock_(start_time),
+      deadline_(Timestamp::PlusInfinity()),
+      callback_([] {}) {}
+
+Clock* FakeAlarm::GetClock() {
+  return &clock_;
+}
+
+bool FakeAlarm::ScheduleAlarmAt(Timestamp deadline) {
+  if (deadline < deadline_) {
+    deadline_ = deadline;
+    return true;
+  }
+  return false;
+}
+
+void FakeAlarm::SetCallback(std::function<void()> callback) {
+  callback_ = callback;
+}
+
+void FakeAlarm::Sleep(TimeDelta duration) {
+  Timestamp end_time = clock_.CurrentTime() + duration;
+
+  while (deadline_ <= end_time) {
+    clock_.AdvanceTime(deadline_ - clock_.CurrentTime());
+    deadline_ = Timestamp::PlusInfinity();
+    callback_();
+  }
+
+  clock_.AdvanceTime(end_time - clock_.CurrentTime());
+}
+
+TEST(CreateTimeControllerTest, CreatesNonNullController) {
+  FakeAlarm alarm(Timestamp::ms(100));
+  EXPECT_NE(CreateTimeController(&alarm), nullptr);
+}
+
+}  // namespace
+}  // namespace webrtc