Pass base layer frame to upper layer decoder if inter-layer prediction is enabled and encoder dropped upper layer. Bug: none Change-Id: I4d13790caabd6469fc0260d8c0ddcb3dabbfb86e Reviewed-on: https://webrtc-review.googlesource.com/65980 Commit-Queue: Sergey Silkin <ssilkin@webrtc.org> Reviewed-by: Rasmus Brandt <brandtr@webrtc.org> Cr-Commit-Position: refs/heads/master@{#22762}