How to remove chromium-browser settings from Ubuntu 14.04?

Execute these commands in terminal :

sudo apt-get remove chromium --purge
rm -rf ~/.config/chromium
rm -rf ~/.cache/chromium
sudo rm -rf /etc/chromium

You don't need to uninstall/reinstall the browser.

To delete the settings for a given user, you must delete the config folder for that user (placed in its home, as a hidden folder, thus the . at the start of the name).

You may delete that folder using the terminal or you may open the home folder in Nautilus and press Ctrl+H to show the hidden files and folders, then delete the folder you want to delete as you would do with any other file.

This prevents you from using rm -rf variations in which a small typo can have serious consequences.