GitLab

Add a new method to allow a DialogDelegate to provide a custom
amount to use as the minimum padding between the extra view and the
button strip in the dialog.
Use this to adjust the padding in the extension uninstall dialog.

BUG=441377

Review URL: https://codereview.chromium.org/1141253002

Cr-Commit-Position: refs/heads/master@{#330622}