Cast: Avoid retransmit if we sent the same packet recently (less than RTT)

media/cast/transport/pacing/paced_sender.h

Index: media/cast/transport/pacing/paced_sender.h
diff --git a/media/cast/transport/pacing/paced_sender.h b/media/cast/transport/pacing/paced_sender.h
index 2373fb59664d0a91f2747792b58860302ce3497f..4d0f71ac3a4fcebdb09e9f8e619e2bc3f0a3287f 100644
--- a/media/cast/transport/pacing/paced_sender.h
+++ b/media/cast/transport/pacing/paced_sender.h
@@ -41,7 +41,8 @@ typedef std::vector<std::pair<PacketKey, PacketRef> > SendPacketVector;
 class PacedPacketSender {
  public:
   virtual bool SendPackets(const SendPacketVector& packets) = 0;
-  virtual bool ResendPackets(const SendPacketVector& packets) = 0;
+  virtual bool ResendPackets(const SendPacketVector& packets,
+                             base::TimeDelta rtt) = 0;
   virtual bool SendRtcpPacket(uint32 ssrc, PacketRef packet) = 0;
   virtual void CancelSendingPacket(const PacketKey& packet_key) = 0;
 
@@ -72,7 +73,8 @@ class PacedSender : public PacedPacketSender,
 
   // PacedPacketSender implementation.
   virtual bool SendPackets(const SendPacketVector& packets) OVERRIDE;
-  virtual bool ResendPackets(const SendPacketVector& packets) OVERRIDE;
+  virtual bool ResendPackets(const SendPacketVector& packets,
+                             base::TimeDelta rtt) OVERRIDE;
   virtual bool SendRtcpPacket(uint32 ssrc, PacketRef packet) OVERRIDE;
   virtual void CancelSendingPacket(const PacketKey& packet_key) OVERRIDE;
 
@@ -108,7 +110,8 @@ class PacedSender : public PacedPacketSender,
   // Returns the next packet to send. RTCP packets have highest priority,
   // resend packets have second highest priority and then comes everything
   // else.
-  PacketRef GetNextPacket(PacketType* packet_type);
+  PacketRef GetNextPacket(PacketType* packet_type,
+                          PacketKey* packet_key);
 
   base::TickClock* const clock_;  // Not owned by this class.
   LoggingImpl* const logging_;    // Not owned by this class.
@@ -117,6 +120,8 @@ class PacedSender : public PacedPacketSender,
   uint32 audio_ssrc_;
   uint32 video_ssrc_;
   std::map<PacketKey, std::pair<PacketType, PacketRef> > packet_list_;
+  std::map<PacketKey, base::TimeTicks> sent_time_;
+  std::map<PacketKey, base::TimeTicks> sent_time_buffer_;
 
   // Maximum burst size for the next three bursts.
   size_t max_burst_size_;