[Cast] Repair receiver playout time calculations and frame skip logic.

media/cast/cast_defines.h

Index: media/cast/cast_defines.h
diff --git a/media/cast/cast_defines.h b/media/cast/cast_defines.h
index b0f9370186e9e60e2cd0a7dc0f8032d603ea4e4a..2084e1c743c3f41edf7a5eaaf06cc1a1bcbb4ebe 100644
--- a/media/cast/cast_defines.h
+++ b/media/cast/cast_defines.h
@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include <limits>
 #include <map>
 #include <set>
 
@@ -135,13 +136,21 @@ inline base::TimeDelta ConvertFromNtpDiff(uint32 ntp_delay) {
   return base::TimeDelta::FromMilliseconds(delay_ms);
 }
 
-inline void ConvertTimeToFractions(int64 time_us,
+inline void ConvertTimeToFractions(int64 ntp_time_us,
                                    uint32* seconds,
                                    uint32* fractions) {
-  DCHECK_GE(time_us, 0) << "Time must NOT be negative";
-  *seconds = static_cast<uint32>(time_us / base::Time::kMicrosecondsPerSecond);
+  DCHECK_GE(ntp_time_us, 0) << "Time must NOT be negative";
+  const int64 seconds_component =
+      ntp_time_us / base::Time::kMicrosecondsPerSecond;
+  // NTP time will overflow in the year 2036.  Also, make sure unit tests don't
+  // regress and use an origin past the year 2036.  If this overflows here, the
+  // inverse calculation fails to compute the correct TimeTicks value, throwing
+  // off the entire system.

[hubbe, 2014/05/19 17:52:20]

Maybe put a DCHECK(ntp_time_us is less than the year 2035) to auto-break this
one year before the deadline? :)

Hopefully this code is dead and buried by then, but if it not, we could at least
give the poor schmuck who is working on it then a year to fix it...

[miu, 2014/05/23 03:09:01]

Done.

+  CHECK(seconds_component <= std::numeric_limits<uint32>::max());
+  *seconds = static_cast<uint32>(seconds_component);
   *fractions = static_cast<uint32>(
-      (time_us % base::Time::kMicrosecondsPerSecond) * kMagicFractionalUnit);
+      (ntp_time_us % base::Time::kMicrosecondsPerSecond) *
+          kMagicFractionalUnit);
 }
 
 inline void ConvertTimeTicksToNtp(const base::TimeTicks& time,