We should remove the hack in ConfiguredActionbarSectionDefinition#setAvailability, always setting section availability for multiple selection to true.
In effect, we cannot simply remove it because most—if not all—content-apps are misconfigured.
The multiple property is never configured, for sections intended for multi-selection.
So multi-selection would result in an empty action bar.
Besides, as quirky as this is, we don't want to change behavior that could potentially affect apps for existing customers.
- We fix the UI def, extend it with a deprecated one (with the hack), and register it as default type-mapping.
- This way, the hack moves to a deprecated class, and we can eventually phase it out at some point in the future.
- We don't try to address potential usages in apps, not much worth the pain. Instead, action bar config may be re-evaluated (different ticket).