Revert of Rename RTPVideoHeader.isFirstPacket to .is_first_packet_in_frame.

webrtc/modules/video_coding/test/stream_generator.cc

Index: webrtc/modules/video_coding/test/stream_generator.cc
diff --git a/webrtc/modules/video_coding/test/stream_generator.cc b/webrtc/modules/video_coding/test/stream_generator.cc
index 73362c732dff52d3659104e8c1ff3db2a005bb40..a33ec9a432a04f07a873bb7b2999a3f3b024319a 100644
--- a/webrtc/modules/video_coding/test/stream_generator.cc
+++ b/webrtc/modules/video_coding/test/stream_generator.cc
@@ -62,11 +62,11 @@
   packet.seqNum = sequence_number;
   packet.timestamp = timestamp;
   packet.frameType = type;
-  packet.is_first_packet_in_frame = first_packet;
+  packet.isFirstPacket = first_packet;
   packet.markerBit = marker_bit;
   packet.sizeBytes = size;
   packet.dataPtr = packet_buffer_;
-  if (packet.is_first_packet_in_frame)
+  if (packet.isFirstPacket)
     packet.completeNALU = kNaluStart;
   else if (packet.markerBit)
     packet.completeNALU = kNaluEnd;