rtcp::Nack packet moved into own file and got Parse function

Review URL: https://codereview.webrtc.org/1461623003

Cr-Commit-Position: refs/heads/master@{#11111}

webrtc/modules/rtp_rtcp/source/rtcp_packet/rtpfb.h

@@ -0,0 +1,48 @@
+/*
+ *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ *
+ */
+
+#ifndef WEBRTC_MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_RTPFB_H_
+#define WEBRTC_MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_RTPFB_H_
+
+#include "webrtc/base/basictypes.h"
+#include "webrtc/modules/rtp_rtcp/source/rtcp_packet.h"
+
+namespace webrtc {
+namespace rtcp {
+
+// RTPFB: Transport layer feedback message.
+// RFC4585, Section 6.2
+class Rtpfb : public RtcpPacket {
+ public:
+  static const uint8_t kPacketType = 205;
+
+  Rtpfb() : sender_ssrc_(0), media_ssrc_(0) {}
+  virtual ~Rtpfb() {}
+
+  void From(uint32_t ssrc) { sender_ssrc_ = ssrc; }
+  void To(uint32_t ssrc) { media_ssrc_ = ssrc; }
+
+  uint32_t sender_ssrc() const { return sender_ssrc_; }
+  uint32_t media_ssrc() const { return media_ssrc_; }
+
+ protected:
+  static const size_t kCommonFeedbackLength = 8;
+  void ParseCommonFeedback(const uint8_t* payload);
+  void CreateCommonFeedback(uint8_t* payload) const;
+
+ private:
+  uint32_t sender_ssrc_;
+  uint32_t media_ssrc_;
+};
+
+}  // namespace rtcp
+}  // namespace webrtc
+#endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_RTPFB_H_