iron-icon is not incompatible with my version

[feidudu1]

<iron-icon icon="paper-dropdown-menu:arrow-drop-down" suffix="" slot="suffix"></iron-icon>

the icon will not show, but if I change it to

<iron-icon icon="arrow-drop-down" suffix="" slot="suffix"></iron-icon>

the icon will show
how did i realize it with configuration？

[feidudu1]

solve：must install 'paper-dropdown-menu'

[Juravenator]

the icon you mentioned is actually declared in the code. And the dependency to paper-dropdown-menu is in bower.json.

So now I'm curious how this was missing for you.

[feidudu1]

because i import "../bower_components/iron-icons/iron-icons.html"
not "../bower_components/iron-icon/iron-icon.html"
so
icon="arrow-drop-down" is valide and show
icon="paper-dropdown-menu:arrow-drop-down" is not valide