Details: * Add RTCNetworkType enum * Add network_type to local ice candidate stats Bug: webrtc:8435 Change-Id: Idb872849c09ad49c8f759d02afdc825e397afa07 Reviewed-on: https://webrtc-review.googlesource.com/14680 Commit-Queue: Gary Liu <qinghualiu@google.com> Reviewed-by: Henrik Boström <hbos@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20822}