Implemented ScopedFakeTime, faking rtc::TimeNanos.

webrtc/base/faketime.h

+/*
+ *  Copyright 2009 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_BASE_FAKETIME_H_
+#define WEBRTC_BASE_FAKETIME_H_
+
+#include "webrtc/base/checks.h"
+#include "webrtc/base/timeutils.h"
+
+namespace rtc {
+namespace test {
+class FakeTime : public FakeTimeInterface {
+ public:
+  explicit FakeTime(uint64_t start_time) : current_time_ns_(start_time) {}
+  uint64_t TimeNanos() override {
+    rtc::CritScope cs(&time_lock_);
+    return current_time_ns_;
+  }
+  void AdvanceTime(uint64_t interval) {
+    rtc::CritScope cs(&time_lock_);
+    current_time_ns_ += interval;
+  }
+ private:
+  CriticalSection time_lock_;
+  uint64_t current_time_ns_ GUARDED_BY(time_lock_);
+};
+
+class ScopedFakeTime : public FakeTime {
+ public:
+  explicit ScopedFakeTime(uint64_t start_time) : FakeTime(start_time) {
+    rtc::test::SetFakeTime(this);
+  }
+  ScopedFakeTime() : ScopedFakeTime(rtc::TimeNanos()) {}

[pbos-webrtc, 2016/05/31 22:35:35]

Is this one useful or added prematurely?

[nisse-webrtc, 2016/06/01 07:35:35]

It's all a bit premature, the unittest uses both constructors. Not clear which
variant is most useful. And I'm fine with keeping this on hold until we've
identified one test to use it. It's not clear to me if it's needed for testing
cl https://codereview.webrtc.org/2017443003/ or not.

+
+  ~ScopedFakeTime() {
+    rtc::test::SetFakeTime(nullptr);
+  }
+};
+
+}  // namespace test
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_FAKETIME_H_