Fix favicon/title badge count

This was using a separate function (in MatrixChat) that didn't
take into account whether we were supposed to be hiding the badge
for rooms so would include notifs that were hidden everywhere else.

Also make it a function & put it in RoomNotifs with all its friends.

Fixes https://github.com/vector-im/riot-web/issues/3060

src/RoomNotifs.js

@@ -35,6 +35,27 @@ function _shouldShowMentionBadge(roomNotifState) {
     return roomNotifState !== MUTE;
 }
 
+export function countRoomsWithNotif(rooms) {
+    return rooms.reduce((result, room, index) => {
+        const roomNotifState = getRoomNotifsState(room.roomId);
+        const highlight = room.getUnreadNotificationCount('highlight') > 0;
+        const notificationCount = room.getUnreadNotificationCount();
+
+        const notifBadges = notificationCount > 0 && _shouldShowNotifBadge(roomNotifState);
+        const mentionBadges = highlight && _shouldShowMentionBadge(roomNotifState);
+        const isInvite = room.hasMembershipState(MatrixClientPeg.get().credentials.userId, 'invite');
+        const badges = notifBadges || mentionBadges || isInvite;
+
+        if (badges) {
+            result.count++;
+            if (highlight) {
+                result.highlight = true;
+            }
+        }
+        return result;
+    }, {count: 0, highlight: false});
+}
+
 export function aggregateNotificationCount(rooms) {
     return rooms.reduce((result, room, index) => {
         const roomNotifState = getRoomNotifsState(room.roomId);