In particular, this allows us to have a SSLCertChain(std::vector<std::unique_ptr<SSLCertificate>>) constructor that avoids making a copy. Bug: webrtc:8289 Change-Id: If353ad886a73aecff98b2939db15c40ada6b4474 Reviewed-on: https://webrtc-review.googlesource.com/4361 Commit-Queue: David Benjamin <davidben@webrtc.org> Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20093}