[Cast] In Audio/VideoSender, drop frames when too-long a duration is in-flight.

media/cast/sender/rtp_timestamp_helper.cc

Index: media/cast/sender/rtp_timestamp_helper.cc
diff --git a/media/cast/sender/rtp_timestamp_helper.cc b/media/cast/sender/rtp_timestamp_helper.cc
index ea0c35c66fbf130d3b41d55b69eb4930b0d4bcbf..9367f8d6a79dca6334bdfb60c40ea693f3ec949f 100644
--- a/media/cast/sender/rtp_timestamp_helper.cc
+++ b/media/cast/sender/rtp_timestamp_helper.cc
@@ -4,6 +4,8 @@
 
 #include "media/cast/sender/rtp_timestamp_helper.h"
 
+#include "media/cast/cast_defines.h"
+
 namespace media {
 namespace cast {
 
@@ -15,17 +17,26 @@ RtpTimestampHelper::RtpTimestampHelper(int frequency)
 RtpTimestampHelper::~RtpTimestampHelper() {
 }
 
-bool RtpTimestampHelper::GetCurrentTimeAsRtpTimestamp(
-    const base::TimeTicks& now, uint32* rtp_timestamp) const {
+bool RtpTimestampHelper::EstimateRtpTimestamp(
+    const base::TimeTicks& t, uint32* rtp_timestamp) const {
   if (last_capture_time_.is_null())
     return false;
-  const base::TimeDelta elapsed_time = now - last_capture_time_;
-  const int64 rtp_delta =
-      elapsed_time * frequency_ / base::TimeDelta::FromSeconds(1);
+  const base::TimeDelta elapsed_time = t - last_capture_time_;
+  const int64 rtp_delta = TimeDeltaToRtpDelta(elapsed_time, frequency_);
   *rtp_timestamp = last_rtp_timestamp_ + static_cast<uint32>(rtp_delta);
   return true;
 }
 
+bool RtpTimestampHelper::EstimateTimeTicks(
+    uint32 rtp_timestamp, base::TimeTicks* t) const {
+  if (last_capture_time_.is_null())
+    return false;
+  const int32 rtp_delta =
+      static_cast<int32>(rtp_timestamp - last_rtp_timestamp_);
+  *t = last_capture_time_ + RtpDeltaToTimeDelta(rtp_delta, frequency_);
+  return true;
+}
+
 void RtpTimestampHelper::StoreLatestTime(
     base::TimeTicks capture_time, uint32 rtp_timestamp) {
   last_capture_time_ = capture_time;