Add a ParseHeader method to RtcpPacket, for parsing common RTCP header.

webrtc/modules/rtp_rtcp/source/rtcp_packet.h

 /*
  *  Copyright (c) 2014 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.
  *
  */
@@ skipping 81 matching lines @@
                            PacketReadyCallback* callback) const;
 
  protected:
   RtcpPacket() {}
 
   virtual bool Create(uint8_t* packet,
                       size_t* index,
                       size_t max_length,
                       PacketReadyCallback* callback) const = 0;
 
-  void CreateHeader(uint8_t count_or_format,
-                    uint8_t packet_type,
-                    size_t length,
-                    uint8_t* buffer,
-                    size_t* pos) const;
+  static void CreateHeader(uint8_t count_or_format,
+                           uint8_t packet_type,
+                           size_t block_length,  // Size in 32bit words - 1.
+                           uint8_t* buffer,
+                           size_t* pos);
 
   bool OnBufferFull(uint8_t* packet,
                     size_t* index,
                     RtcpPacket::PacketReadyCallback* callback) const;
 
   virtual size_t BlockLength() const = 0;
   size_t HeaderLength() const;
 
   static const size_t kHeaderLength = 4;
 
@@ skipping 1038 matching lines @@
 
  private:
   const size_t buffer_length_;
   size_t length_;
   rtc::scoped_ptr<uint8_t[]> buffer_;
 };
 
 }  // namespace rtcp
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_RTP_RTCP_RTCP_PACKET_H_