Disables the Google+ "Add to Circles" buttons in Gmail.
Removes the "Add to Circles" button in Gmail that Google+ has added in. These buttons normally appear on mouseover of a contact's name.
All it takes is accidentally mousing over one to activate it (for example, while your mouse is on its way to the "Emails" link for a contact), which rolls out a list of Circles, covering up whatever UI was underneath it. If you then mistakenly check one of those Circles, you've just sent an awkward Google+ invite to that contact.
Uses a simple CSS selector and no JS, and restricts itself to load only on Gmail pages, so it shouldn't harm performance.
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