It started today after my scheduled system updates which required a reboot. Right after starting the browser I noticed that something is strange and the title bar, fonts and everything else looks smaller.
After opening the inspector I noticed the resolution in the browser is 2560x1440 instead of 1920x1080 but the zoom factor is still at 100%.
I have not found directly a solution but there appears to be a similar issue on Ubuntu 16.04: https://superuser.com/questions/1116767/chrome-ui-size-zoom-levels-in-ubuntu-16-04
To quickly test this out make sure you closed all Chrome instances (killall chrome) and run the following command:
/usr/bin/google-chrome-stable --force-device-scale-factor=1
It worked for me, because for some reason after the updates Chrome started detecting the device scale of 0.75 which is set by gnome-tweaks.
In order to apply the change to the chrome started you need to edit the google-chrome.desktop file:
sudo gedit /usr/share/applications/google-chrome.desktop
Find the following commands:
Exec=/usr/bin/google-chrome-stable %U
Exec=/usr/bin/google-chrome-stable
Exec=/usr/bin/google-chrome-stable --incognito
and add the --force-device-scale-factor property to each of them:
Exec=/usr/bin/google-chrome-stable --force-device-scale-factor=1 %U
Exec=/usr/bin/google-chrome-stable --force-device-scale-factor=1
Exec=/usr/bin/google-chrome-stable --force-device-scale-factor=1 --incognito
If you have Chrome as a favorite in the dock make sure to remove it and add it again to replace any cached values.