Remove hardcoded kValueSizeBytes values from variable-length header extensions.

webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc b/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
index b89aefef53e44977f2bda96438bd16cb3b4572af..30cd1abe2fd464038f7e64d549978c6813746b20 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
@@ -33,6 +33,13 @@ namespace webrtc {
 namespace {
 constexpr size_t kRedForFecHeaderLength = 1;
 
+constexpr RTPExtensionSizeInfo kFecExtensionSizes[] = {

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

how this list is different from kExtensionSizes in rtp_sender.cc ?

may be add an accessor to RTPSender:
static rtc::ArrayView<> ???ExtensionSizes();

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

Done, I've added a getter for the FEC packets.

Also, since RtpHeaderLength() might be used for other packets later on, I
figured it'd make sense for it to have an |extension_sizes| arg instead of using
kExtensionSizes directly.

[danilchap, 2017/05/09 12:33:49]

Do you know such packets?
It is generally better to make code simpler now and add complexity only when you
about to use it.

[erikvarga1, 2017/05/09 13:30:30]

Alright, since it's not used elsewhere, I guess it makes more sense to have the
function work for the padding/fec packets only. I removed the extra arg and just
added a comment instead.

+    CreateExtensionSizeInfo<AbsoluteSendTime>(),
+    CreateExtensionSizeInfo<TransmissionOffset>(),
+    CreateExtensionSizeInfo<TransportSequenceNumber>(),
+    CreateExtensionSizeInfo<PlayoutDelayLimits>(),
+};
+
 void BuildRedPayload(const RtpPacketToSend& media_packet,
                      RtpPacketToSend* red_packet) {
   uint8_t* red_payload = red_packet->AllocatePayload(
@@ -249,7 +256,7 @@ void RTPSenderVideo::GetUlpfecConfig(int* red_payload_type,
 
 size_t RTPSenderVideo::CalculateFecPacketOverhead() const {
   if (flexfec_enabled())
-    return flexfec_sender_->MaxPacketOverhead();
+    return flexfec_sender_->MaxPacketOverhead(kFecExtensionSizes);
 
   size_t overhead = 0;
   if (red_enabled()) {