andybons: Does Polygerrit team have any tips to share regarding performance issues with Paper, or how to best approach replacing them with custom implementations? 

ChOps service frontend maintainers seem to have a shared need for lightweight, high-performance, information-dense Polymer components (these needs are apparently at odds with Paper/Material Design goals).

+ Lots of nested elements kills performance. Lots of nested _custom_ elements kills performance even more.
+ As the components are meant to be generalizable, the amount of features they need to support is typically larger than if you built a one-off. This is not to say generalizability is bad, but it’s something to think about and weigh against other options.
+ You should take a look at the Material High Density spec to see if it helps you at all.

Thanks for the feedback and pointers, Andy! I dug around the PolyGerrit source code some for study, and I noticed it looks like you don't use any Paper elements (but plenty of iron ones) for PolyGerrit. Is this correct? 

For Sheriff-o-Matic, right now we have a lot of paper-inputs, paper-buttons, etc everywhere, so I think replacing those with mostly HTML equivalents + some simple CSS should help. I think for buttons and such, there'd be no need to make a full custom Polymer element. 

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/f4ee02e1f8ab76903627003f0f92344c57ed479a

commit f4ee02e1f8ab76903627003f0f92344c57ed479a
Author: Tiff Zhang <zhangtiff@google.com>
Date: Wed May 17 19:11:18 2017

SoM: Start removing paper elements and adjust styling.

Bug:720084
Bug:720021

Change-Id: Idc821a25d27a9e1cf43b6ee78606c3c837733c32
Reviewed-on: https://chromium-review.googlesource.com/506615
Commit-Queue: Tiffany Zhang <zhangtiff@chromium.org>
Reviewed-by: Sean McCullough <seanmccullough@chromium.org>

[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-drawer/som-drawer.js
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-alert-item/som-alert-item.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-drawer/som-drawer.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-app/som-app.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-annotations/som-annotations.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-tree-status/som-tree-status.html
[add] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-input-styles.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-master-restarts/som-master-restarts.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/bower.json
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-header-styles.html