Change to calculate the real NTP in TimeTicks.

media/cast/cast_ntp_tick_clock.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/cast/cast_ntp_tick_clock.h"
+
+namespace media {
+namespace cast {
+
+// Network Time Protocol (NTP), which is in seconds relative to 0h UTC on
+// 1 January 1900.
+static const int64 kNtpEpochDeltaSeconds = GG_INT64_C(9435484800);
+
+// January 1970, in NTP seconds.
+// Network Time Protocol (NTP), which is in seconds relative to 0h UTC on
+// 1 January 1900.
+static const int64 kUnixEpochInNtpSeconds = GG_INT64_C(2208988800);
+
+
+CastNtpTickClock::CastNtpTickClock() {
+  SetTickClock(&default_tick_clock_);
+}
+
+CastNtpTickClock::~CastNtpTickClock() {}
+
+void CastNtpTickClock::SetTickClock(base::TickClock* tick_clock) {
+  tick_clock_ = tick_clock;
+}
+
+// Ticks relative to 0h UTC on 1 January 1900.
+base::TimeTicks CastNtpTickClock::NowTicks() {
+  base::TimeDelta ticks_and_time_offset_at_unix_epoch =
+      base::TimeTicks::UnixEpoch() - base::TimeTicks();
+  base::TimeTicks elapsed_since_unix_epoch = tick_clock_->NowTicks() -
+      ticks_and_time_offset_at_unix_epoch;
+
+  return elapsed_since_unix_epoch +
+      base::TimeDelta::FromSeconds(kUnixEpochInNtpSeconds);
+}
+
+}  // namespace cast
+}  // namespace media
+