Reland of Rename RTPVideoHeader.isFirstPacket to .is_first_packet_in_frame.

webrtc/modules/video_coding/packet_buffer.cc

Index: webrtc/modules/video_coding/packet_buffer.cc
diff --git a/webrtc/modules/video_coding/packet_buffer.cc b/webrtc/modules/video_coding/packet_buffer.cc
index 03aeb5a4a9691e7fd867aada0b97628e272fd71c..bbf488cc0e22400ca5849ded6f2cc6279b9a0e57 100644
--- a/webrtc/modules/video_coding/packet_buffer.cc
+++ b/webrtc/modules/video_coding/packet_buffer.cc
@@ -103,7 +103,7 @@ bool PacketBuffer::InsertPacket(VCMPacket* packet) {
     if (AheadOf(seq_num, last_seq_num_))
       last_seq_num_ = seq_num;
 
-    sequence_buffer_[index].frame_begin = packet->isFirstPacket;
+    sequence_buffer_[index].frame_begin = packet->is_first_packet_in_frame;
     sequence_buffer_[index].frame_end = packet->markerBit;
     sequence_buffer_[index].seq_num = packet->seqNum;
     sequence_buffer_[index].continuous = false;