This extension could be useful, but I think it needs some improvement:

There are no instructions or screenshots for the database management application. The path to the database is also undocumented, and does not appear to be user-configurable. (What if you want to store the log on a network file server?)

It would be nice to have a log player extension in the browser instead of a separate Python application, since many platforms do not have a Python interpreter installed by default. That would enable live browser mirroring for tech support and classroom applications without the need for a VNC server (which consumes more bandwidth on the host PC's data link).

It appears that Mozilla is working on a similar project and I mention it here so that duplication of effort towards the same goal can be avoided:

https://developer.mozilla.org/en-US/docs/Mozilla/Projects/WebReplay
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/WebReplayRoadmap