WebUI: cr-dialog, add cr-dialog-open event and update tests to use new event

Bug: 860699
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: I16d40d0b7dbebffc6af6cf88d8f82cda39f42d47
Reviewed-on: https://chromium-review.googlesource.com/1130501
Commit-Queue: Esmael El-Moslimany <aee@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573866}
6 files changed