Basic support for notification payloads in the panel.

Line-item veto is there, but allows you to cancel some
notifications you probably shouldn't be canceling. (Should
hide the "X" in those cases.)

No preference given to "sticky" notifications, because
there's no such thing yet.

Notifications are now limited to 4 visible icons, per spec.
The implementation is a total hack for now.

Change-Id: Ibdf433ae94189117f983c510fe5e0cff0bf5c44c

services/java/com/android/server/NotificationManagerService.java

@@ -61,6 +61,7 @@ import android.util.Log;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityManager;
 import android.widget.Toast;
+import android.widget.Toast;
 
 import java.io.FileDescriptor;
 import java.io.PrintWriter;
@@ -280,6 +281,10 @@ class NotificationManagerService extends INotificationManager.Stub
                     Notification.FLAG_FOREGROUND_SERVICE);
         }
 
+        public void onNotificationClear(String pkg, String tag, int id) {
+            cancelNotification(pkg, tag, id, 0, 0); // maybe add some flags?
+        }
+
         public void onPanelRevealed() {
             synchronized (mNotificationList) {
                 // sound