Widgets: Only scroll to the newly clicked-and-added widget if it is out of the viewport.

props shaunandrews.
see #25821.


git-svn-id: https://develop.svn.wordpress.org/trunk@26695 602fd350-edb4-49c9-b593-d223f7449a82
Widgets: Add click-to-add widgets to the bottom (not top) of the target sidebar.

fixes #25821.


git-svn-id: https://develop.svn.wordpress.org/trunk@26696 602fd350-edb4-49c9-b593-d223f7449a82