GitLab

This CL:
* Changes the dialog modal type if it's anchored.
* Removes the extension name from dialog header getter call, as
corresponding string doesn't require it anymore.
* Adds the ability to skip confirmation dialog, as it's complicated to
interact with the dialog from the browser tests.

Bug: 1128197
Change-Id: Ie830049dde68398f605fd59025c7f4c985e3434b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2421673Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Nikita Podguzov <nikitapodguzov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809284}