Avoids potential rounding of -inf time delta in TaskQueuePacedSender.

This rounding triggers a dcheck that crashes debug builds.

Furtunately, in release mode this does not matter as the resulting
value is anyway capped to 0.

Unfortunately, it is almost impossible to write a test for this even
with simulated time as the conditions needed to trigger this condition
includes thread scheduling being slightly off in such a way that an
unscheduled process call preempts a scheduled one at a time when
sending a sufficiently large padding packet becomes possible - and
right after starting a new probe cluster.

We should consider updating this class to make unit testing easier.

Bug: webrtc:10809
Change-Id: I533e6e716bddc106d11e82a9e3edb4e0035fd21c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/192786
Reviewed-by: Per Kjellander <[email protected]>
Commit-Queue: Erik Språng <[email protected]>
Cr-Commit-Position: refs/heads/master@{#32589}

Author: Erik Språng

modules/pacing/task_queue_paced_sender.cc

@@ -224,9 +224,13 @@ void TaskQueuePacedSender::MaybeProcessPackets(
     // If we're probing and there isn't already a wakeup scheduled for the next
     // process time, always post a task and just round sleep time down to
     // nearest millisecond.
-    time_to_next_process =
-        std::max(TimeDelta::Zero(),
-                 (next_process_time - now).RoundDownTo(TimeDelta::Millis(1)));
+    if (next_process_time.IsMinusInfinity()) {
+      time_to_next_process = TimeDelta::Zero();
+    } else {
+      time_to_next_process =
+          std::max(TimeDelta::Zero(),
+                   (next_process_time - now).RoundDownTo(TimeDelta::Millis(1)));
+    }
   } else if (next_process_time_.IsMinusInfinity() ||
              next_process_time <= next_process_time_ - hold_back_window_) {
     // Schedule a new task since there is none currently scheduled