Yes, there's code in Chromium going back to the KDE/ Konqueror and WebKit days that's LGPL licensed. Mostly in the Blink rendering engine like you linked.
Just to clarify the relevant thing is whether Google owns the copyright to Chromium source, and it does for a huge part. It can license that code however it wants, including open source, or no license at all.
Chrome/Chromium also uses a ton of open source libraries for which Google does NOT hold the copyright, but all of them, per their license, can be linked with closed source code and distributed (i.e. they are not GPL/copyleft).
Chromium is BSD licensed so Google absolutely can just make it closed source.