Reintroduce priority to notification sorting order.

Bug: 27387966
Change-Id: I7de7c4688c9774c2dbd9ea7f2c69566cb66b7285
diff --git a/services/core/java/com/android/server/notification/NotificationComparator.java b/services/core/java/com/android/server/notification/NotificationComparator.java
index 5e4703d..7dff2c1 100644
--- a/services/core/java/com/android/server/notification/NotificationComparator.java
+++ b/services/core/java/com/android/server/notification/NotificationComparator.java
@@ -28,10 +28,11 @@
         final int leftImportance = left.getImportance();
         final int rightImportance = right.getImportance();
         if (leftImportance != rightImportance) {
-            // by priority, high to low
+            // by importance, high to low
             return -1 * Integer.compare(leftImportance, rightImportance);
         }
 
+        // Whether or not the notification can bypass DND.
         final int leftPackagePriority = left.getPackagePriority();
         final int rightPackagePriority = right.getPackagePriority();
         if (leftPackagePriority != rightPackagePriority) {
@@ -39,6 +40,13 @@
             return -1 * Integer.compare(leftPackagePriority, rightPackagePriority);
         }
 
+        final int leftPriority = left.sbn.getNotification().priority;
+        final int rightPriority = right.sbn.getNotification().priority;
+        if (leftPriority != rightPriority) {
+            // by priority, high to low
+            return -1 * Integer.compare(leftPriority, rightPriority);
+        }
+
         final float leftPeople = left.getContactAffinity();
         final float rightPeople = right.getContactAffinity();
         if (leftPeople != rightPeople) {