More RecoverableSecurityException docs.

Mention convenience methods in class docs, and require a valid
NotificationChannel to be provided to match O best-practices.

Also mention that notifyChange() should be triggered when the action
is finished.

Test: builds, boots
Bug: 34676491
Change-Id: I0e6c6d43a93cbce1a5de02621290cc2ff9423274
diff --git a/api/system-removed.txt b/api/system-removed.txt
index bd535d2..640dc81 100644
--- a/api/system-removed.txt
+++ b/api/system-removed.txt
@@ -4,6 +4,10 @@
     method public deprecated void setLatestEventInfo(android.content.Context, java.lang.CharSequence, java.lang.CharSequence, android.app.PendingIntent);
   }
 
+  public final class RecoverableSecurityException extends java.lang.SecurityException implements android.os.Parcelable {
+    method public deprecated void showAsNotification(android.content.Context);
+  }
+
 }
 
 package android.app.admin {