Send ranking update on importance change.

            final int N = mNotificationList.size();

            ArrayList<String> orderBefore = new ArrayList<String>(N);

            int[] visibilities = new int[N];

            int [] importances = new int[N];

            for (int i = 0; i < N; i++) {

                final NotificationRecord r = mNotificationList.get(i);

                orderBefore.add(r.getKey());

                visibilities[i] = r.getPackageVisibilityOverride();

                importances[i] = r.getImportance();

                mRankingHelper.extractSignals(r);

            }

            mRankingHelper.sort(mNotificationList);

            for (int i = 0; i < N; i++) {

                final NotificationRecord r = mNotificationList.get(i);

                if (!orderBefore.get(i).equals(r.getKey())

                        || visibilities[i] != r.getPackageVisibilityOverride()) {

                        || visibilities[i] != r.getPackageVisibilityOverride()

                        || importances[i] != r.getImportance()) {

                    scheduleSendRankingUpdate();

                    return;

                }