Misc truncation fixes for gn builds with VS 2015

chrome/browser/media/webrtc_rtp_dump_writer.cc

Index: chrome/browser/media/webrtc_rtp_dump_writer.cc
diff --git a/chrome/browser/media/webrtc_rtp_dump_writer.cc b/chrome/browser/media/webrtc_rtp_dump_writer.cc
index 06e6e8b65e65103263c7fb7d7b68cab6da3fec9b..f5871d493397ec6f54deae6aa703bb80678062d3 100644
--- a/chrome/browser/media/webrtc_rtp_dump_writer.cc
+++ b/chrome/browser/media/webrtc_rtp_dump_writer.cc
@@ -306,7 +306,8 @@ void WebRtcRtpDumpWriter::WriteRtpPacket(const uint8* packet_header,
     FlushBuffer(incoming, false, FlushDoneCallback());
 
   WritePacketDumpHeaderBigEndian(
-      start_time_, packet_dump_length, packet_length, dest_buffer);
+      start_time_, base::checked_cast<uint16>(packet_dump_length),
+      base::checked_cast<uint16>(packet_length), dest_buffer);
 
   // Writes the actual RTP packet header.
   AppendToBuffer(packet_header, header_length, dest_buffer);