[Cast] Cleanup: Remove TransportXXXXXSender, an unnecessary layer of indirection.

media/cast/transport/cast_transport_sender.h

 // 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.
 
-// This is the main interface for the cast transport sender. The cast sender
-// handles the cast pipeline from encoded frames (both audio and video), to
-// encryption, packetization and transport.
+// This is the main interface for the cast transport sender.  It accepts encoded
+// frames (both audio and video), encrypts their encoded data, packetizes them
+// and feeds them into a transport (e.g., UDP).
 
 // Construction of the Cast Sender and the Cast Transport Sender should be done
 // in the following order:
 // 1. Create CastTransportSender.
 // 2. Create CastSender (accepts CastTransportSender as an input).
 // 3. Call CastTransportSender::SetPacketReceiver to ensure that the packets
 //    received by the CastTransportSender will be sent to the CastSender.
 // Steps 3 can be done interchangeably.
 
 // Destruction: The CastTransportSender is assumed to be valid as long as the
@@ skipping 52 matching lines @@
   virtual void InitializeVideo(const CastTransportVideoConfig& config) = 0;
 
   // Sets the Cast packet receiver. Should be called after creation on the
   // Cast sender. Packets won't be received until this function is called.
   virtual void SetPacketReceiver(
       const PacketReceiverCallback& packet_receiver) = 0;
 
   // The following two functions handle the encoded media frames (audio and
   // video) to be processed.
   // Frames will be encrypted, packetized and transmitted to the network.
   virtual void InsertCodedAudioFrame(const EncodedFrame& audio_frame) = 0;

[hubbe, 2014/06/03 22:42:22]

How about replacing these two functions with
InsertCodedFrame(const EncodedFrame& frame, int ssrc) = 0;
?

[miu, 2014/06/03 23:32:55]

Good idea, but I'd like to reserve this for a later change.  Changing this
interface means doing a bunch of work in each subclass.

   virtual void InsertCodedVideoFrame(const EncodedFrame& video_frame) = 0;
 
   // Builds an RTCP packet and sends it to the network.
   // |ntp_seconds|, |ntp_fraction| and |rtp_timestamp| are used in the
   // RTCP Sender Report.
   virtual void SendRtcpFromRtpSender(uint32 packet_type_flags,
                                      uint32 ntp_seconds,
                                      uint32 ntp_fraction,
                                      uint32 rtp_timestamp,
                                      const RtcpDlrrReportBlock& dlrr,
                                      uint32 sending_ssrc,
                                      const std::string& c_name) = 0;
 
   // Retransmission request.
   virtual void ResendPackets(
       bool is_audio,
       const MissingFramesAndPacketsMap& missing_packets) = 0;
 };
 
 }  // namespace transport
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_TRANSPORT_CAST_TRANSPORT_SENDER_H_