Remove hardcoded kValueSizeBytes values from variable-length header extensions.

webrtc/modules/rtp_rtcp/source/rtp_sender.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_sender.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender.cc b/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
index 6fdac6f63fb08507ec68781c4bff1e59b6ca693e..5bb5474f17835512d01ee2b815d2fe8c19a86414 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
@@ -45,6 +45,13 @@ constexpr int kBitrateStatisticsWindowMs = 1000;
 
 constexpr size_t kMinFlexfecPacketsToStoreForPacing = 50;
 
+constexpr RTPExtensionSizeInfo kExtensionSizes[] = {

[danilchap, 2017/05/08 16:25:06]

can you add a comment or change variable name to explain why only these
extensions are selected. (e.g. why PlayoutDelay is included, but AudioLevel and
VideoOrientation are not).

[erikvarga1, 2017/05/09 11:40:03]

Done. I've renamed this to show that it can be used for padding or FEC packets.

+    CreateExtensionSizeInfo<AbsoluteSendTime>(),
+    CreateExtensionSizeInfo<TransmissionOffset>(),
+    CreateExtensionSizeInfo<TransportSequenceNumber>(),
+    CreateExtensionSizeInfo<PlayoutDelayLimits>(),
+};
+
 const char* FrameTypeToString(FrameType frame_type) {
   switch (frame_type) {
     case kEmptyFrame:
@@ -961,7 +968,8 @@ size_t RTPSender::RtpHeaderLength() const {
   rtc::CritScope lock(&send_critsect_);
   size_t rtp_header_length = kRtpHeaderLength;
   rtp_header_length += sizeof(uint32_t) * csrcs_.size();
-  rtp_header_length += rtp_header_extension_map_.GetTotalLengthInBytes();
+  rtp_header_length +=
+      rtp_header_extension_map_.GetTotalLengthInBytes(kExtensionSizes);
   return rtp_header_length;
 }