Add InvalidArgument error type for NotificationDatabase.

content/browser/notifications/notification_database.h

Index: content/browser/notifications/notification_database.h
diff --git a/content/browser/notifications/notification_database.h b/content/browser/notifications/notification_database.h
index 00fae877dae125856affdd46707b08559227d108..5cc9ea93a27d82e50039795a1f8f63293b875ab8 100644
--- a/content/browser/notifications/notification_database.h
+++ b/content/browser/notifications/notification_database.h
@@ -61,9 +61,12 @@ class CONTENT_EXPORT NotificationDatabase {
     // leveldb operation not supported
     STATUS_NOT_SUPPORTED = 5,
 
+    // Invalid database ID or snapshot ID provided.
+    STATUS_INVALID_ARGUMENT = 6,

[Peter Beverloo, 2016/06/21 11:00:33]

Please update the NotificationDatabaseStatus enumeration in histograms.xml.

+
     // Number of entries in the status enumeration. Used by UMA. Must always be
     // one higher than the otherwise highest value in this enumeration.
-    STATUS_COUNT = 6
+    STATUS_COUNT = 7
   };
 
   explicit NotificationDatabase(const base::FilePath& path);