Type extension does not work anymore in Polymer 2:
https://polymer-library.polymer-project.org/2.0/docs/about_20#type-extension
Recommendation by Polyer expert was:
Most of the time, you can do
<iron-input params...>
<input is="iron-input" thoseSameParams...>
</iron-input>
id attributes were kept at the <input> element, not moved to the
<iron-input> element. This may mean that in Polymer 2 some still tests
are still failing that look up input elements by id. Will fix this in
a follow-up change.
The goal was to create a simple non-breaking change across the entire
code base. There might still be some issues running this with Polymer 2.
This change also clean ups iron-input html imports. Some could be
removed, some had to be added.
Change-Id: I48361ff465990246622ec8ad23d80b75f40cc055
540a5fe0bb