[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 77 matching lines @@
   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_