Having ScopedFieldTrials at class scope might introduce some hard to understand lifetime patterns. Keeping them in scope only for the Run method simplifies that, reducing the risk of problems. Bug: b/197053062 Change-Id: I1c1239757387443552a7b5f83f68014ee56e4248 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/229920 Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org> Reviewed-by: Artem Titov <titovartem@webrtc.org> Cr-Commit-Position: refs/heads/main@{#34836}