Allocate std::map in-place and capture pointer to it by Obj-C lambda. Bug: None Change-Id: I285d8b2d10fef9130a5d0e457ad3982ff8a1f00f Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/375920 Commit-Queue: Yury Yarashevich <yura.yaroshevich@gmail.com> Reviewed-by: Kári Helgason <kthelgason@webrtc.org> Cr-Commit-Position: refs/heads/main@{#43840}