Implement a solution to work around the visual defect brought by the lazy loading strategy of iron-list

The use case is the one from WEBUI-338: as it is not considered as a bug but as a side-effect of the lazy loading strategy of the iron-list component, we need a solution to display results while scrolling without this visual defect.

It sounds that it's a known issue from iron-list: https://github.com/PolymerElements/iron-list/issues/481

Is the solution to be able to reset the data when we scroll?

Or should we implement another solution based on a default thumbnail?

Or can we push to have a better behavior from iron-list?