This is used to allow using a pre-configured builders as arguments to
fixture code.
Bug: webrtc:9510
Change-Id: I7837d284580fdbc926535ce5b2d8f582056534ce
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161948
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30070}