TaskQueueManagerPerfTest to also test immediate tasks

I was curious about the cost of locking in TaskQueueImpl and realised
we don't have coverage for non-delayed PostTask so I added one.

Change-Id: I765f3d4316e9e6c7bac01d7b2f3a1d02188a2185
Reviewed-on: https://chromium-review.googlesource.com/1065776
Reviewed-by: Alexander Timin <[email protected]>
Commit-Queue: Alex Clarke <[email protected]>
Cr-Commit-Position: refs/heads/master@{#560253}
1 file changed