email field appears twice with contribution forms that have Drupal account registration

Contribution pages that include a profile with Drupal account registration enabled result in the email field being displayed twice (see "contribute:transact" image). This situation is correctly handled on the Drupal user registration page by removing profile's email field (see "user:registration" image).

To recreate:
1. Create a profile that allows Drupal account registration. Add the email field to the profile, which is required for this option, and at least one other field. Enable all "User for" options.
2. Create a contribution form that uses this profile.
3. Visit the live contribution page and see that the Contribution page's default email shows up at the top, but the proile's email field is then also shown in the profile section. (e.g. "contribut:transact" image attached)
4. Visit the Drupal user registration page and see that the profile's email field is removed since the default Drupal email field is already present (e.g. "user:registration" image)

One suggested resolution:
When a profile appears on a Contribution page and has Drupal account registration enabled all email addresses in the profile should be hidden. The email address entered in the default contribution form is copied into the contribution email fields before saving.