Apply diff view cookie on compare

## What does this MR do?

Correctly respects the code view changing when comparing 2 refs.

## What are the relevant issue numbers?

Closes #19573 

## Screenshots (if relevant)

![Screen_Shot_2016-07-07_at_12.38.07](/uploads/b6da78cc2bbc2c79dbe8292037176c1a/Screen_Shot_2016-07-07_at_12.38.07.png)

![Screen_Shot_2016-07-07_at_12.38.17](/uploads/977f8b697c65bdb1701db11a39287ac6/Screen_Shot_2016-07-07_at_12.38.17.png)

See merge request !5135