Adds tracing specifically to Close, for creating streams and also moves tracing for SetLocal/RemoteDescription from WebRtcSession. Also adding some tracing in ChannelManager to see what's taking time inside Close. BUG=webrtc:5167 R=tommi@webrtc.org Review URL: https://codereview.webrtc.org/1509903002 . Cr-Commit-Position: refs/heads/master@{#10943}