Code review comment for lp:~uriboni/webbrowser-app/larger-close-tab-button

With this change the area looks correct on mobile, but it’s not on desktop.

To verify that, I added a semi-transparent red rectangle that fills the abstract button, and this is how it looks:

 - on desktop: http://people.canonical.com/~osomon/tab-close-button-desktop.png
 - on mobile: http://people.canonical.com/~osomon/tab-close-button-mobile.png

On desktop, the area shouldn’t cover the entire height of the tab, it should be limited to the height of the X icon. And the horizontal center of the area and that of the X icon should be aligned.