Right now the type of previews is served only logged when the user opt out by dismissing the info bar, or the navigation is finished.
It would be nice to log which type of previews is served on the page. An easy way is to log the message whenever the infobar is created, and use the infobar's previews type to see which type of previews is it.
Comment 1 by thanhdle@chromium.org
, Nov 1 2017