Keep scrollPos for every file in commit diff dialog

Steps to repro the issue:
1. Open the commit diff dialog (from history) of a commit with multiple bigger changes (I took 5b4e64cb8b36759e8863d78f68975698106689f4)
2. Scroll down in one file
3. Switch to another file -> The scrollbar is on the same position
4. Scroll up in that file -> The scrollbar changes for every other file