Added A/V sync tests with drifting clocks.

webrtc/test/drifting_clock.cc

+/*
+ *  Copyright (c) 2016 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 "webrtc/test/drifting_clock.h"
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+namespace test {
+
+DriftingClock::DriftingClock(Clock* clock, float drift)
+    : clock_(clock), drift_(drift), start_time_(-1) {
+  RTC_CHECK(clock);
+  RTC_CHECK_GT(drift, -1.);

[stefan-webrtc, 2016/02/09 14:02:20]

I think all of these float constants should be -1.f or -1.0f

[danilchap, 2016/02/09 14:56:49]

Done.

+  start_time_ = clock_->TimeInMicroseconds();
+}
+
+float DriftingClock::Drift() const {
+  return (clock_->TimeInMicroseconds() - start_time_) * drift_;

[stefan-webrtc, 2016/02/09 14:02:20]

DCHECK that start_time_ >= 0 here.

[danilchap, 2016/02/09 14:56:49]

But start_time_ is set in the constructor 3 lines above. it does not have
invalid values.

[stefan-webrtc, 2016/02/10 13:20:52]

Ah, my mistake. Good that you moved it to the initializer list.

+}
+
+int64_t DriftingClock::TimeInMilliseconds() const {
+  return clock_->TimeInMilliseconds() + Drift() / 1000.;
+}
+
+int64_t DriftingClock::TimeInMicroseconds() const {
+  return clock_->TimeInMicroseconds() + Drift();
+}
+
+void DriftingClock::CurrentNtp(uint32_t& seconds, uint32_t& fractions) const {
+  const double kNtpFracPerMicroSecond = 4294.967296;  // = 2^32 / 10^6
+
+  clock_->CurrentNtp(seconds, fractions);
+  uint64_t totalfractions = (static_cast<uint64_t>(seconds) << 32) | fractions;

[stefan-webrtc, 2016/02/09 14:02:20]

total_fractions

[danilchap, 2016/02/09 14:56:49]

Done.

+  totalfractions += Drift() * kNtpFracPerMicroSecond;
+  seconds = totalfractions >> 32;
+  fractions = static_cast<uint32_t>(totalfractions);
+}
+
+int64_t DriftingClock::CurrentNtpInMilliseconds() const {
+  return clock_->CurrentNtpInMilliseconds() + Drift() / 1000.;
+}
+}  // namespace test
+}  // namespace webrtc