Retransmissions are supposed to be sent before normal packets by the pacer, but the current implementation will only use it if the second packet is a retransmission and the first packet is not. It misses the case where the first packet is retransmission and the second packet is not.
This CL fixes the comparator and adds a unit test.
Also changed the SendAndExpectPacket function to propagate the retransmission flag to the expectations. Previously, all packets were expected to be normal packets.
BUG=webrtc:6124
Review-Url: https://codereview.webrtc.org/2156063004
Cr-Commit-Position: refs/heads/master@{#13502}
f39f7d931c