Code review comment for lp:~alan-griffiths/mir/fix-1603922

I know our design docs use the word 'tip' but that doesn't make it ideal. I'm aiming for something that existing toolkit developers will understand. They will grep for 'tooltip' and never find it.

Remember the Mir API should be a superset of the Unity design in order to support other shells and existing desktop concepts that are omitted from the Unity design.

We should not be betting on Unity8 being the winning shell. Because if it doesn't get sufficient traction and Mir is not more flexible than the Unity design, then Mir too will suffer as a platform that can't support other shells.