In a couple of places in the UI, we show superimposed icons on buttons to execute an operation (called "Extra Icons" internally). Hovering them would show the tooltip of the underlying button, which is misleading and confusing.
There are cases where it's not obvious what an icon does, so a tooltip would be quite useful here. It's likely we are going to use superimposed icons in more places in the future, e.g. see D11890.
Screenshots (mouse cursor is not visible, but it's hovering the icons):
The extra icon basically acts as an override for the button in the tooltip code.
This patch comes from rB2250b5cefee7 with an improvement to also get the operator description for the tooltip. rather than the button's regular description.


