Reland "Avoid calling OnRoundTripTimeUpdate with invalid RTTs."

This is a reland of afa61c94e50e2737d4d4b22d7a830845e763cf27

Original change's description:
> Avoid calling OnRoundTripTimeUpdate with invalid RTTs.
> 
> Bug: none
> Change-Id: Ic19b87ad7094465da6091d0e99b10a6d1b7d2e58
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/128776
> Commit-Queue: Christoffer Rodbro <crodbro@webrtc.org>
> Reviewed-by: Sebastian Jansson <srte@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#27308}

Bug: none
Change-Id: Ic5669a27ea66ab0c207556c54bb595c83850ffd3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/129924
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Christoffer Rodbro <crodbro@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27315}

call/rtp_transport_controller_send.cc

diff --git a/call/rtp_transport_controller_send.cc b/call/rtp_transport_controller_send.cc
index a414c3b..ab95907 100644
--- a/call/rtp_transport_controller_send.cc
+++ b/call/rtp_transport_controller_send.cc
@@ -400,7 +400,7 @@
     report.receive_time = Timestamp::ms(now_ms);
     report.round_trip_time = TimeDelta::ms(rtt_ms);
     report.smoothed = false;
-    if (controller_)
+    if (controller_ && !report.round_trip_time.IsZero())
       PostUpdates(controller_->OnRoundTripTimeUpdate(report));
   });
 }