Updating an unpublished draft post in quick-edit mode sets the post's publish date

[uxtremist]

Problem:

• If you update an unpublished draft post in quick-edit mode, the post's publish date is saved.
  
• Then, later on, when you actually publish the post, its publish date is incorrect.

Suggested fix:

• If the post is a draft, do not automatically set the post's publish date in quick-edit mode.

Steps to reproduce:

(1) Go to WP-Admin -> Posts.

(2) Create and save a new post. Make sure you click "Save Draft" — not "Publish".

(3) Note that the post is marked as "Publish immediately"; that is, it has no publish date.

(4) Go back to WP-Admin -> Posts.

(5) Hover your pointer over the post you just created. Click "Quick Edit".

— Note that in the panel that appears, the "Date" field is automatically set to [the current date and time].

(6) Click "Update" in quick-edit mode.

(7) Hover your pointer over the post you just updated. Click "Edit".

— Note that in the Edit Post page that appears, the post is now marked as "Publish on: [the date and time from step (5)]"

Has been this way since Quick Edit was introduced in 2.7 (#8144).

The problem is that edit_date is true by default:
http://core.trac.wordpress.org/browser/tags/3.3.1/wp-admin/js/inline-edit-post.dev.js#L238
And the condition for $clear_date in wp_update_post() is not satisfied:
http://core.trac.wordpress.org/browser/tags/3.3.1/wp-includes/post.php#L2693

19907.patch​ brings the similar check and comment into edit_post().

19907.2.patch​ sets edit_date to false (doesn't touch post_date_gmt).

I don't know that I'd call it major, since it's been there since 2.7, but the desired behavior is that when using quick edit when a post is a draft, it should adjust 'last edited' not 'publish' time.

Closely related, #16985.

Needs unit tests. Thinking punt.

Related: #22350