Convert a few lingering DFATALs to QUIC_BUG. Not flag protected.

net/quic/core/quic_packet_creator.cc

Index: net/quic/core/quic_packet_creator.cc
diff --git a/net/quic/core/quic_packet_creator.cc b/net/quic/core/quic_packet_creator.cc
index 285ad708ea6491e8c75f8b2c2a2b3712d52120d4..27f715a66b371aa5ac3416dc8322eea32f9ff2b5 100644
--- a/net/quic/core/quic_packet_creator.cc
+++ b/net/quic/core/quic_packet_creator.cc
@@ -318,12 +318,13 @@ void QuicPacketCreator::ReserializeAllFrames(
   // Serialize the packet and restore packet number length state.
   for (const QuicFrame& frame : retransmission.retransmittable_frames) {
     bool success = AddFrame(frame, false);
-    LOG_IF(DFATAL, !success)
-        << " Failed to add frame of type:" << frame.type
-        << " num_frames:" << retransmission.retransmittable_frames.size()
-        << " retransmission.packet_number_length:"
-        << retransmission.packet_number_length
-        << " packet_.packet_number_length:" << packet_.packet_number_length;
+    QUIC_BUG_IF(!success) << " Failed to add frame of type:" << frame.type
+                          << " num_frames:"
+                          << retransmission.retransmittable_frames.size()
+                          << " retransmission.packet_number_length:"
+                          << retransmission.packet_number_length
+                          << " packet_.packet_number_length:"
+                          << packet_.packet_number_length;
   }
   SerializePacket(buffer, buffer_len);
   packet_.original_path_id = retransmission.path_id;