Manage Watches user list content extends past field drop down

Summary

When adding users to the Manage Watchers "Watching this space" or "Watching this page", the content of the user list drop down extends past the field if the username is longer than 26 characters.

Steps to Reproduce

• Go to a page > Manage Watchers> Add User (add users who have a username longer than 26 characters)

Expected Results

The drop down adjusts to the username size or has a longer character limit, and doesn't force the text outside of the drop down.  

Actual Results

Longer usernames are forced outside of the drop down box and overlay the usernames below.

Workaround

No work around at this time.