The pacing controller allowed sending bitrate probes, despite it being paused. This CL adresses that, and makes sure the task-queue based mode also properly repsects pausing. Bug: webrtc:10809 Change-Id: I79643c9a24666110d7583fce3ed1bfd6865e9e10 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/162520 Reviewed-by: Florent Castelli <orphis@webrtc.org> Commit-Queue: Erik Språng <sprang@webrtc.org> Cr-Commit-Position: refs/heads/master@{#30109}