Adds RTCCertificate, a reference counted object indirectly owning an SSLCertificate (by owning the SSLIdentity).

BUG=webrtc:4927
R=tommi@chromium.org, tommi@webrtc.org, torbjorng@webrtc.org

Review URL: https://codereview.webrtc.org/1299223002 .

Cr-Commit-Position: refs/heads/master@{#9741}
4 files changed