Sometimes scrolling to the top is nice. Sometimes not so much.
Example where it's not right:
1. Navigate to a change screen with a long commit message, e.g. https://gerrit-review.googlesource.com/c/72567/?polygerrit=1
2. Scroll down to find the file list
3. Click a file to go to diff screen
4. Go back (eventually 'u') to the change screen, then navigate to the next file in the list.
Expected: viewport is where I left it, scrolled down so I can see a file list
Actual: jumped back to the top so I have to scroll down again
Mergedinto: 3715