Steps to replicate the issue (include links if applicable):

• Start editing a long page
• Turn CodeMirror on
• Scroll to bottom (Ctrl+End)
• Enter something
• Do an undo (Ctrl+Z)
• Scroll to top (Ctrl+Home)
• Do a redo (Ctrl+Y)
• Do an undo (Ctrl+Z)

What happens?:
The cursor goes to top (and so does the scroll view), so it's not clear what was just undone.

What should have happened instead?:
The cursor stays adjacent to the chunk that was changed, so it's clear what was just undone.