Add method FilenameWithParams to TestConfig. Bug: none Change-Id: I9f683e661537148dc01bee25f7510938fa656dc5 Reviewed-on: https://webrtc-review.googlesource.com/21382 Reviewed-by: Rasmus Brandt <brandtr@webrtc.org> Commit-Queue: Åsa Persson <asapersson@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20651}