Cast: cancel re-sending if a later nack packet says the receiver doesn't want it anymore

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 fccd0b5625b4fd745f87bb857f350005dc021232..2373fb59664d0a91f2747792b58860302ce3497f 100644
--- a/media/cast/transport/pacing/paced_sender.h
+++ b/media/cast/transport/pacing/paced_sender.h
@@ -43,6 +43,7 @@ class PacedPacketSender {
   virtual bool SendPackets(const SendPacketVector& packets) = 0;
   virtual bool ResendPackets(const SendPacketVector& packets) = 0;
   virtual bool SendRtcpPacket(uint32 ssrc, PacketRef packet) = 0;
+  virtual void CancelSendingPacket(const PacketKey& packet_key) = 0;
 
   virtual ~PacedPacketSender() {}
 
@@ -73,6 +74,7 @@ class PacedSender : public PacedPacketSender,
   virtual bool SendPackets(const SendPacketVector& packets) OVERRIDE;
   virtual bool ResendPackets(const SendPacketVector& packets) OVERRIDE;
   virtual bool SendRtcpPacket(uint32 ssrc, PacketRef packet) OVERRIDE;
+  virtual void CancelSendingPacket(const PacketKey& packet_key) OVERRIDE;
 
  private:
   // Actually sends the packets to the transport.