Change to calculate the real NTP in TimeTicks.

media/cast/cast_ntp_tick_clock.cc

Index: media/cast/cast_ntp_tick_clock.cc
diff --git a/media/cast/cast_ntp_tick_clock.cc b/media/cast/cast_ntp_tick_clock.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e67733b583e0f366d17363d1b8c33297a50b6989
--- /dev/null
+++ b/media/cast/cast_ntp_tick_clock.cc
@@ -0,0 +1,38 @@
+// 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);
+
+CastNtpTickClock::CastNtpTickClock()
+    : tick_clock_(&default_tick_clock_) {
+  // Start time in NTP time; which have its epoch at year 1900.
+  base::Time start_time_ntp =
+     base::Time::Now() - base::TimeDelta::FromSeconds(kNtpEpochDeltaSeconds);
+
+  base::TimeTicks start_time_ntp_in_ticks =
+     base::TimeTicks::FromInternalValue(start_time_ntp.ToInternalValue());
+
+  start_offset_ = start_time_ntp_in_ticks - base::TimeTicks::Now();
+}
+
+CastNtpTickClock::~CastNtpTickClock() {}
+
+void CastNtpTickClock::SetTickClock(base::TickClock* tick_clock) {
+  tick_clock_ = tick_clock;

[miu, 2013/10/23 18:24:02]

start_offset_ needs to be recalculated here.  Perhaps you can just move all the
ctor code into here, and have the ctor call this method?

[pwestin, 2013/10/23 21:07:49]

Done.

+}
+
+base::TimeTicks CastNtpTickClock::NowTicks() {
+  return tick_clock_->NowTicks() + start_offset_;
+}
+
+}  // namespace cast
+}  // namespace media
+