Oops, "custom-iconsets" from my message is not a thing. I just meant that we should create custom iconsets, using iron-iconset-svg. Thanks!

Last update :-) I simplified things so you don't have to worry about that poly-icon URL anymore. If you've already started this work, just note that the comment in custom icon files is shorter now:

      <!--
      These icons are copied from Polymer's iron-icons and kept in sorted order.
      See http://goo.gl/Y1OdAq for instructions on adding additional icons.
      -->

https://codereview.chromium.org/1992503002/

Thank you for the update!
I'll remove iron-icons for M52.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/be3e68926a236bfaaf85240efd1e034733e7699b

commit be3e68926a236bfaaf85240efd1e034733e7699b
Author: fukino <fukino@chromium.org>
Date: Wed May 18 08:58:46 2016

Files app: Use custom iron-iconset-svg for iron-icons.

BUG= 612068 
TEST=manually confirmed the replaced icons.

Review-Url: https://codereview.chromium.org/1990803003
Cr-Commit-Position: refs/heads/master@{#394365}

[modify] https://crrev.com/be3e68926a236bfaaf85240efd1e034733e7699b/ui/file_manager/file_manager/foreground/elements/elements_bundle.html
[add] https://crrev.com/be3e68926a236bfaaf85240efd1e034733e7699b/ui/file_manager/file_manager/foreground/elements/icons.html
[modify] https://crrev.com/be3e68926a236bfaaf85240efd1e034733e7699b/ui/file_manager/file_manager/foreground/js/import_controller.js
[modify] https://crrev.com/be3e68926a236bfaaf85240efd1e034733e7699b/ui/file_manager/file_manager/foreground/js/ui/combobutton.js
[modify] https://crrev.com/be3e68926a236bfaaf85240efd1e034733e7699b/ui/file_manager/file_manager/main.html
[modify] https://crrev.com/be3e68926a236bfaaf85240efd1e034733e7699b/ui/file_manager/file_manager_resources.grd

@fukino Hi, trying to verify this bug. Could you please provide test steps to verify?

This doesn't include any user-visible change, so I think we can mark this as Verified by comment#5 (the commit message)

Thanks fukino@.

Marking verified as per comment#5