Revert of Rename RTPVideoHeader.isFirstPacket to .is_first_packet_in_frame.

webrtc/modules/rtp_rtcp/source/rtp_receiver_video.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_receiver_video.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_receiver_video.cc b/webrtc/modules/rtp_rtcp/source/rtp_receiver_video.cc
index d6c5e5c29b6ac4667f80681c0df5322d645747a1..4f79ea9e56944bfaa670f1267b777a0bc8174724 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_receiver_video.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_receiver_video.cc
@@ -82,7 +82,7 @@
     return -1;
   }
 
-  rtp_header->type.Video.is_first_packet_in_frame = is_first_packet;
+  rtp_header->type.Video.isFirstPacket = is_first_packet;
   RtpDepacketizer::ParsedPayload parsed_payload;
   if (!depacketizer->Parse(&parsed_payload, payload, payload_data_length))
     return -1;