Increase the size of address bar and tabs bar in Google Chrome: screen res. 1920×1080, 15" LCD screen
Solution 1:
I had the same problem and got it fixed from Ubuntu setting. Setting -> Universal Access -> Seeing -> Large text (by default its off, turn it on)
Solution 2:
@Apoorv Pontis answer does scale fonts, but at best it's a hack. It is equivalent to lowering your display resolution by the same factor (although it allows more finer increments).
Using a 4k display (3840px wide) and starting with font scale of 1.0. Go into Chrome developer tools and select the element of the page. It will measure 3840px wide. Now using Gnome tweaks, change font scaling to 2.0. Again use Chrome developer tools and select the element. You will see it is now about 1920px wide with some round off error in scaling.
This not only scales the fonts but the entire content of the browser by a factor of 2.0. Using other things, you will see you effectively downgraded your 4K display to HD 1920 x 1080 for your entire desktop.
From what I have seen from Arch Linux wiki, looks like this uses something similar to what xrandr does.
For everything, but Chrome its better to adjust font sizes than using this font scaling feature. If you use a shell theme, you can also adjust font size of the shell font for the top bar. Do that by editing the appropriate .CSS file for the theme.
It appears the only way to fix Chromes address bar is to dig into the source code. Everything else obeys font size but that. It appears to be fixed tiny for some reason.
Solution 3:
As suggested by user DK Bose in the comments, this question gave me the correct solution. But in Ubuntu 18.10, the scaling factor can be found/changed by installing Gnome Tweaks and then navigating to the 'Fonts' tab.