Remove hardcoded kValueSizeBytes values from variable-length header extensions.

webrtc/modules/rtp_rtcp/source/rtp_sender.h

Index: webrtc/modules/rtp_rtcp/source/rtp_sender.h
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender.h b/webrtc/modules/rtp_rtcp/source/rtp_sender.h
index dc35a038e1de6f9d09cc24eec04ff326f6e039c0..b0165c628da023c9a8925ffb63e410ece64b2f2d 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender.h
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender.h
@@ -17,6 +17,7 @@
 #include <vector>
 
 #include "webrtc/api/call/transport.h"
+#include "webrtc/base/array_view.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/criticalsection.h"
 #include "webrtc/base/deprecation.h"
@@ -71,9 +72,6 @@ class RTPSender {
   uint32_t FecOverheadRate() const;
   uint32_t NackOverheadRate() const;
 
-  // Excluding size of RTP and FEC headers.
-  size_t MaxPayloadSize() const;
-
   int32_t RegisterPayload(const char* payload_name,
                           const int8_t payload_type,
                           const uint32_t frequency,
@@ -148,6 +146,9 @@ class RTPSender {
 
   void SetRtxPayloadType(int payload_type, int associated_payload_type);
 
+  // Size info for header extensions used by FEC packets.
+  static rtc::ArrayView<const RtpExtensionSize> FecExtensionSizes();
+
   // Create empty packet, fills ssrc, csrcs and reserve place for header
   // extensions RtpSender updates before sending.
   std::unique_ptr<RtpPacketToSend> AllocatePacket() const;
@@ -156,6 +157,7 @@ class RTPSender {
   // Return false if sending was turned off.
   bool AssignSequenceNumber(RtpPacketToSend* packet);
 
+  // Used for padding and FEC packets only.
   size_t RtpHeaderLength() const;
   uint16_t AllocateSequenceNumber(uint16_t packets_to_send);
   // Including RTP headers.