Yup, Chrome/Chromium has a checkbox in the settings interface to "Use system titlebar and borders". Disabling that removes the sytem titlebar which is useless for a browser and thus adds a precious 20 pixels over the entire width of the browser window.
Opera (still) not featuring this setting in Linux keeps me from switching to Opera from Chromium as default browser. I really love Opera, also on my Android phone, but this is unacceptable to me 
It shouldn't be that hard to enable this I guess...