When resizing an area, the header search fields and data-blocks should be the first things to disappear, not the buttons

An example with the outliner header, note that the search input stays the same width, while the buttons disappear:

I would much rather have the search bar shrink/disappear than having the buttons go.

Same with data-block inputs, like images or materials:

First of all, data-blocks should never be allowed to be that long :P

Second, they should collapse before any of the other ui elements in the header.