IDBObjectStore's constructor should be responsible for messaging the IndexedDB thread

[rasviitanen]

When creating an IDBObjectStore in IDBDatabase's CreateObjectStore function, a message is sent to the idb thread that makes sure that we create/open a store in our database as well. It makes more sense to send this message from the constructor of IDBObjectStore.

Files
compontents/script/dom/idbdatabase.rs
compontents/script/dom/idbobjectstore.rs