Moreover, it doesn't seem like static linking to me.
A similar example would be using a GPLv3 licensed JavaScript library in a website. What it implies to other HTML/JS/CSS code is controversial [0]. The FSF actually believed that they should not be "infected" [1], and the legal implications may need to be tested in court.
The FSF question is about templates, but the chrome extension in question also seems to have copied nontrivial JS.
I don't think chrome extensions can be modified by the user; there's probably some integrity check. So to be GPL compliant they need to publish source files to rebuild the extension?
A similar example would be using a GPLv3 licensed JavaScript library in a website. What it implies to other HTML/JS/CSS code is controversial [0]. The FSF actually believed that they should not be "infected" [1], and the legal implications may need to be tested in court.
[0]: https://opensource.stackexchange.com/q/4360/15873
[1]: https://www.gnu.org/licenses/gpl-faq.en.html#WMS