Notification history improvements

- don't keep readding history list onresume
- remove unstyled background (just use elevation for contrast for now)
- remove summaries from snoozed and recently dimissed because the user
wouldn't have seen their content

Test: manual
Fixes: 149499024
Change-Id: Ie43c752f42a7dfcac5ca9e3d118df07124daf974

src/com/android/settings/notification/history/NotificationSbnAdapter.java

@@ -94,6 +94,13 @@ public class NotificationSbnAdapter extends
     }
 
     public void onRebuildComplete(List<StatusBarNotification> notifications) {
+        // summaries are low content; don't bother showing them
+        for (int i = notifications.size() - 1; i >= 0; i--) {
+            StatusBarNotification sbn = notifications.get(i);
+            if (sbn.isGroup() && sbn.getNotification().isGroupSummary()) {
+                notifications.remove(i);
+            }
+        }
         mValues = notifications;
         notifyDataSetChanged();
     }