[indexeddb] What should happen when specifying the wrong "mode" or "direction"?

We need to define in the spec what should happen if a developers defines an invalid "mode" or "direction".  Do we throw a TypeError Exception or revert to defauls?

FF seems to allow this behavior and reverts back to a readOnly transaction mode and a direction of next, respectively:
* db.transaction( objectStoreList, "invalidMode") ===  db.transaction( objectStoreList)
* o.openCursor(keyRange, "invalidDirection") === o.openCursor(keyRange)

We're okay with this behavior if everyone else agrees.

Israel