Per Polymer 2 migration guide, type extensions are no longer supported, see https://www.polymer-project.org/2.0/docs/upgrade#remove-type-extension-elements.
Currently in Chromium the following elements leverage type extensions.
cr-action-menu (extends dialog)
cr-dialog (extends dialog)
cr-drawer (extends dialog)
cr-lazy-render (extends template)
cr-link-row (extends button)
@calamity: Do you have any cycles to help with cr-action-menu case?
I started a proof-of-concept CL that changes cr-action-menu to not use type extensions anymore, at https://chromium-review.googlesource.com/c/chromium/src/+/944163.
The CL only attempts to migrate a single action menu occurrence (the one at chrome://settings/searchEngines), and to fix the cr-action-menu tests to pass.
The tests that are failing are currently marked with a dummy test2() function.
Status update
[DONE]
cr-drawer
cr-action-menu
[Remaining]
cr-dialog
cr-lazy-render
cr-link-row
@calamity: Re-marking this bug as available. If you start working on any of these (maybe cr-lazy-render maybe?), please mention it here to avoid duplicate work.
Comment 1 by dpa...@chromium.org
, Mar 2 2018