Prior to this change, the VideoProcessor was run on the main thread in the unit tests. Using a TaskQueue there instead, we can be stricter in the thread checks. Bug: webrtc:8524 Change-Id: Ice7b68f7344fc52801dff7a98cbc219b7231bfbc Reviewed-on: https://webrtc-review.googlesource.com/48921 Reviewed-by: Sergey Silkin <ssilkin@webrtc.org> Commit-Queue: Rasmus Brandt <brandtr@webrtc.org> Cr-Commit-Position: refs/heads/master@{#21942}