The overlap in functionality is quite limited and separating the functionality makes it a bit easier to follow each. This prepares for adding a SimulatedThread class in a follow up CL. Bug: webrtc:11255 Change-Id: I83c754bd570113dfb582098bb4d39e27bb4f4d87 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/165688 Reviewed-by: Jonas Olsson <jonasolsson@webrtc.org> Commit-Queue: Sebastian Jansson <srte@webrtc.org> Cr-Commit-Position: refs/heads/master@{#30229}