Ensure that frame_buffer_controller_ does not get assigned null by the factory. Bug: None Change-Id: I84e141ae0390cd024863f88cdcdc79b8b13e7c64 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/137043 Reviewed-by: Rasmus Brandt <brandtr@webrtc.org> Commit-Queue: Elad Alon <eladalon@webrtc.org> Cr-Commit-Position: refs/heads/master@{#27962}