media: Cleanup class/struct forward declarations

media/cast/net/rtp/rtp_packetizer.h

 // Copyright 2014 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.
 
 #ifndef MEDIA_CAST_NET_RTP_RTP_PACKETIZER_H_
 #define MEDIA_CAST_NET_RTP_RTP_PACKETIZER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <cmath>
 #include <list>
 #include <map>
 
 #include "base/time/time.h"
 #include "media/cast/common/rtp_time.h"
 #include "media/cast/net/rtp/packet_storage.h"
 
-namespace base {
-class TickClock;
-}
-
 namespace media {
 namespace cast {
 
 class PacedSender;
 
 struct RtpPacketizerConfig {
   RtpPacketizerConfig();
   ~RtpPacketizerConfig();
 
   // General.
@@ skipping 36 matching lines @@
   uint16_t sequence_number_;
 
   size_t send_packet_count_;
   size_t send_octet_count_;
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_NET_RTP_RTP_PACKETIZER_H_