Remove hardcoded kValueSizeBytes values from variable-length header extensions.

webrtc/modules/rtp_rtcp/include/flexfec_sender.h

Index: webrtc/modules/rtp_rtcp/include/flexfec_sender.h
diff --git a/webrtc/modules/rtp_rtcp/include/flexfec_sender.h b/webrtc/modules/rtp_rtcp/include/flexfec_sender.h
index e69daf3ff06b8360b7d4216a689d9e230c0be6a8..a2c7a4ab1ef7f1d1b9ea1bc3b67b319a3051a5f8 100644
--- a/webrtc/modules/rtp_rtcp/include/flexfec_sender.h
+++ b/webrtc/modules/rtp_rtcp/include/flexfec_sender.h
@@ -14,6 +14,7 @@
 #include <memory>
 #include <vector>
 
+#include "webrtc/base/array_view.h"
 #include "webrtc/base/basictypes.h"
 #include "webrtc/base/random.h"
 #include "webrtc/base/sequenced_task_checker.h"
@@ -38,6 +39,7 @@ class FlexfecSender {
                 uint32_t ssrc,
                 uint32_t protected_media_ssrc,
                 const std::vector<RtpExtension>& rtp_header_extensions,
+                rtc::ArrayView<const RtpExtensionSize> extension_sizes,
                 Clock* clock);
   ~FlexfecSender();
 
@@ -79,6 +81,7 @@ class FlexfecSender {
   // Implementation.
   UlpfecGenerator ulpfec_generator_;
   const RtpHeaderExtensionMap rtp_header_extension_map_;
+  const size_t header_extensions_size_;
 };
 
 }  // namespace webrtc