Function SetClockForTesting

webrtc/base/timeutils.cc:35–39

ClockInterface* g_clock = nullptr;

ClockInterface* SetClockForTesting(ClockInterface* clock) {
  ClockInterface* prev = g_clock;
  g_clock = clock;
  return prev;
}

uint64_t SystemTimeNanos() {
  int64_t ticks;