Given the absolute behemoth of scope laid out in the W3C specs, I don't think that's even possible.

https://codetabs.com/count-loc/count-loc-online.html

Using LadybirdBrowser/ladybird & ignoring the following folders:

.devcontainer,.github,Documentation,Tests,Toolchain,Libraries

...Yields about 36k lines of C++. With the libraries, the LOC count balloons to 310k.

If a still-in-alpha browser already has 300k lines of code to deal with, there's very little chance that a spec-compliant browser will be able to do the same within 30k lines.