[rtp_rtcp] rtcp::Empty moved into own file and renamed to CompoundPacket on the way

webrtc/modules/rtp_rtcp/source/rtcp_packet.cc

Index: webrtc/modules/rtp_rtcp/source/rtcp_packet.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_packet.cc b/webrtc/modules/rtp_rtcp/source/rtcp_packet.cc
index 64a69f1029db4759d9b469729345e9d581b7f73d..830dd3acda160bd494a8f4bc99e442f3cec11cdc 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_packet.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_packet.cc
@@ -416,17 +416,6 @@ void RtcpPacket::CreateHeader(
   AssignUWord16(buffer, pos, length);
 }
 
-bool Empty::Create(uint8_t* packet,
-                   size_t* index,
-                   size_t max_length,
-                   RtcpPacket::PacketReadyCallback* callback) const {
-  return true;
-}
-
-size_t Empty::BlockLength() const {
-  return 0;
-}
-
 bool SenderReport::Create(uint8_t* packet,
                           size_t* index,
                           size_t max_length,