Removes RepairedRtpStreamId from overhead calculation.

In https://webrtc-review.googlesource.com/c/src/+/173704 the overhead
calculations were made more static, so that "volatile" extensions
(those that are not set on every packet) are ignored. The intent, as
the comments specify, was to ignore RepairedRtpStreamId since that is
only used on RTX packets.
This CL makes us actually count that extension as volatile.

Bug: webrtc:10809
Change-Id: If42ae84e4c09ff9112e93f8d872ee890c6253a23
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/175010
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31246}

Author: Erik Språng

modules/rtp_rtcp/source/rtp_sender.cc

@@ -110,7 +110,6 @@ bool IsNonVolatile(RTPExtensionType type) {
     case kRtpExtensionTransportSequenceNumber02:
     case kRtpExtensionFrameMarking:
     case kRtpExtensionRtpStreamId:
-    case kRtpExtensionRepairedRtpStreamId:
     case kRtpExtensionMid:
     case kRtpExtensionGenericFrameDescriptor00:
     case kRtpExtensionGenericFrameDescriptor02:
@@ -121,6 +120,7 @@ bool IsNonVolatile(RTPExtensionType type) {
     case kRtpExtensionPlayoutDelay:
     case kRtpExtensionVideoContentType:
     case kRtpExtensionVideoTiming:
+    case kRtpExtensionRepairedRtpStreamId:
     case kRtpExtensionColorSpace:
       return false;
     case kRtpExtensionNone:

modules/rtp_rtcp/source/rtp_sender_unittest.cc

@@ -2032,6 +2032,30 @@ TEST_P(RtpSenderTest, CountMidOnlyUntilAcked) {
   EXPECT_EQ(rtp_sender()->ExpectedPerPacketOverhead(), 12u);
 }
 
+TEST_P(RtpSenderTest, DontCountVolatileExtensionsIntoOverhead) {
+  RtpRtcp::Configuration config;
+  config.clock = &fake_clock_;
+  config.outgoing_transport = &transport_;
+  config.local_media_ssrc = kSsrc;
+  config.retransmission_rate_limiter = &retransmission_rate_limiter_;
+  rtp_sender_context_ = std::make_unique<RtpSenderContext>(config);
+
+  // Base RTP overhead is 12B.
+  EXPECT_EQ(rtp_sender()->ExpectedPerPacketOverhead(), 12u);
+
+  rtp_sender()->RegisterRtpHeaderExtension(kRtpExtensionInbandComfortNoise, 1);
+  rtp_sender()->RegisterRtpHeaderExtension(kRtpExtensionAbsoluteCaptureTime, 2);
+  rtp_sender()->RegisterRtpHeaderExtension(kRtpExtensionVideoRotation, 3);
+  rtp_sender()->RegisterRtpHeaderExtension(kRtpExtensionPlayoutDelay, 4);
+  rtp_sender()->RegisterRtpHeaderExtension(kRtpExtensionVideoContentType, 5);
+  rtp_sender()->RegisterRtpHeaderExtension(kRtpExtensionVideoTiming, 6);
+  rtp_sender()->RegisterRtpHeaderExtension(kRtpExtensionRepairedRtpStreamId, 7);
+  rtp_sender()->RegisterRtpHeaderExtension(kRtpExtensionColorSpace, 8);
+
+  // Still only 12B counted since can't count on above being sent.
+  EXPECT_EQ(rtp_sender()->ExpectedPerPacketOverhead(), 12u);
+}
+
 TEST_P(RtpSenderTest, SendPacketMatchesVideo) {
   std::unique_ptr<RtpPacketToSend> packet =
       BuildRtpPacket(kPayload, true, 0, fake_clock_.TimeInMilliseconds());