src/css/var/getStyles.js

define( function() {
	"use strict";

	return function( elem ) {

		// Support: IE <=11 only, Firefox <=30 (trac-15098, trac-14150)
		// IE throws on elements created in popups
		// FF meanwhile throws on frame elements through "defaultView.getComputedStyle"
		var view = elem.ownerDocument.defaultView;

		if ( !view || !view.opener ) {
			view = window;
		}

		return view.getComputedStyle( elem );
	};
} );