Oilpan: Ship Oilpan for SyncCallbackHelper, CreateFileResult and CallbackWrapper in filesystem/

These are leftovers when we shipped Oilpan for filesystem/ once.

BUG=340522

Review URL: https://codereview.chromium.org/501263003

git-svn-id: svn://svn.chromium.org/blink/trunk@180909 bbb929c8-8fbe-4397-9dbb-9b2b20218538
void EntrySync::trace(Visitor* visitor)
{
    EntryBase::trace(visitor);
}

void EntrySync::trace(Visitor* visitor)
{
    EntryBase::trace(visitor);
}
