Update interfaces/IndexedDB.idl (#13810)

Source: https://github.com/tidoust/reffy-reports/blob/825f02d/whatwg/idl/IndexedDB.idl
Build: https://travis-ci.org/tidoust/reffy-reports/builds/448699564
diff --git a/interfaces/IndexedDB.idl b/interfaces/IndexedDB.idl
index 3982d11..137528c 100644
--- a/interfaces/IndexedDB.idl
+++ b/interfaces/IndexedDB.idl
@@ -50,9 +50,16 @@
                                     optional [EnforceRange] unsigned long long version);
   [NewObject] IDBOpenDBRequest deleteDatabase(DOMString name);
 
+  Promise<sequence<IDBDatabaseInfo>> databases();
+
   short cmp(any first, any second);
 };
 
+dictionary IDBDatabaseInfo {
+  DOMString name;
+  unsigned long long version;
+};
+
 [Exposed=(Window,Worker)]
 interface IDBDatabase : EventTarget {
   readonly attribute DOMString name;