 private let log = Logger.browserLogger
 
 private let ThumbnailIdentifier = "Thumbnail"
+private let FrecencyLimit = 20
 
 extension UIView {
     public class func viewOrientationForSize(size: CGSize) -> UIInterfaceOrientation {

    func notificationReceived(notification: NSNotification) {
        switch notification.name {
        case NotificationFirefoxAccountChanged, NotificationPrivateDataClearedHistory:
            refreshHistory(self.layout.thumbnailCount)
            break
        default:
            // no need to do anything at all

            make.edges.equalTo(self.view)
        }
        self.collection = collection
        self.refreshHistory(FrecencyLimit)
    }

    deinit {
