Use real video duration instead of test duration to calculate harmonic
frame rate in DefaultVideoQualityAnalyzer.
Bug: webrtc:11445
Change-Id: Ia5f96b2f87178419ec6ebe2ff5dbcb5a0c03c824
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/171104
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30854}