GitLab

- Autogenerate Polymer 3 cr-action-menu and test
- Autogenerate modulized focus_row.js, since cr-action-menu depends on
it
- Add cr-action-menu to demo page
- Script changes, required to allow cr-action-menu to export its enum

Bug: 965770
Change-Id: Ie453b1f5f9ebe385143768cac1609ae1ae2f9de3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1789759Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695844}