Fix assert that breaks on certain bots. Bug: webrtc:9228 Change-Id: Ie28ba4a27a4ca07a6877373e41a432ee67eccb1e Reviewed-on: https://webrtc-review.googlesource.com/76441 Commit-Queue: Anders Carlsson <andersc@webrtc.org> Commit-Queue: Magnus Jedvert <magjed@webrtc.org> Reviewed-by: Magnus Jedvert <magjed@webrtc.org> Cr-Commit-Position: refs/heads/master@{#23212}