Simply use
rm -r ~/.config/google-chrome/Default/Web\ Data
or (on Ubuntu 14.10)
rm -r ~/.config/chromium/Default/Web\ Data
or, for the lazy,
l ~/.config/google-chrome/Default/Web\ Data
l ~/.config/chromium/Default/Web\ Data
rm -rf ~/.config/google-chrome/Default/Web\ Data
rm -rf ~/.config/chromium/Default/Web\ Data
* Be careful while using rm -rf
UPDATE
I am really sick of seeing this error and I did this;
Make a file
nano ~/delete-chrome-web-data
Put this in it
#!/usr/bin/env bash
rm -rf ~/.config/chromium/Default/Web\ Data
rm -rf ~/.config/google-chrome/Default/Web\ Data
give the script execute permission
chmod u+x delete-chrome-web-data
And when I see that error, run: sh ~/delete-chrome-web-data