Avoid an expensive attachment counting query on the post editing screen.

Merges [28191], [28194] to the 3.9 branch.

props johnbillion.
fixes #27985.


git-svn-id: https://develop.svn.wordpress.org/branches/3.9@28261 602fd350-edb4-49c9-b593-d223f7449a82
Drag/drop on the editor to upload: don't trigger the uploader when selected text is being dragged from one window to another.

Merges [28189] to the 3.9 branch.

props azaozz.
fixes #27880.


git-svn-id: https://develop.svn.wordpress.org/branches/3.9@28262 602fd350-edb4-49c9-b593-d223f7449a82