This item is similar to paper-item, where it does not really have a reason to exist. It just provides some styling, that can be otherwise applied to normal elements (div or span etc).
We should update usages, and remove it from third_party/polymer. Currently used in the following files (also see [1]):
chrome/browser/resources/chromeos/login/controller-pairing-screen.html
chrome/browser/resources/chromeos/emulator/device_emulator_pages.html
chrome/browser/resources/chromeos/login/host-pairing-screen.html
[1] https://cs.chromium.org/search/?q=paper-icon-item.html+-file:third_party+-file:infra+-file:out/Debug&type=cs
Comment 1 by dpa...@chromium.org
, Jun 25 2018