GitLab

- Autogenerate modulized CrContainerShadowBehavior
- Autogenerate Polymer 3 version of cr-dialog
- Autogenerate Polymer 3 cr-dialog test
- Add cr-dialog to Polymer 3 demo page

Bug: 965770
Change-Id: I6e8c8994b71edb80366cf30f6fff41ed98382722
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1779435
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693318}