to extract byte representation of a built extension without rebuilding it. Bug: webrtc:9361 Change-Id: I5e2a5caeb8ff28dcb58dc25d53407c449c86df44 Reviewed-on: https://webrtc-review.googlesource.com/102940 Reviewed-by: Philip Eliasson <philipel@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#24925}