imip-bar.js / imip-bar-overlay.xul:
The third button will now work as a menu-button, if there are more than 3 possible actions on a itip request. If there are exact 3 actions available, the button will drop its menu type and act as a normal button instead.
More than three actions:
Less then three actions:
After porting the dialog from the inverse source repository, the xul attributes had to be updated to gecko 1.9 attributes to get auto-completion working again.
With this, the immediate GUI updates required for the delegation support should be done and the missing functionality in calItipUtils.jsm will come next.