64e739aeae
Use it to separate UMA e2e delay metric between screenshare from video. Content type extension is set based on encoder settings and processed and decoders. Also, Fix full-stack-tests to calculate RTT correctly, so new metric could be tested. BUG=webrtc:7420 Review-Url: https://codereview.webrtc.org/2772033002 Cr-Commit-Position: refs/heads/master@{#17640}