Skip accounting for small packets and suspend the prober if no large-enough packets have been sent for some time. This especially seems to have triggered in audio-only calls where all packets are too small, making TimeUntilNextProbe return 0 forever, causing the module process thread to wake up forever. BUG=webrtc:5506 R=stefan@webrtc.org Review URL: https://codereview.webrtc.org/1688703002 . Cr-Commit-Position: refs/heads/master@{#11634}