What version are you running?
2.5.3
What's the URL of the page this enhancement relates to, if any?
r/<id>/diff/
Describe the enhancement and the motivation for it.
When working on a review with a large set of changes spread across multiple files it would be very helpful to open the diffs for a single file in a new tab.

For large reviews using the original page with the list of files as just a navigator and not having it show the file diffs at all.
While it is possible to use the browsers "Open in New Tab" capability that just opens the whole review in the new tab scrolled to that point.

The motivation here is NOT to include the diffs for other files or the full review header area.
It isn't unusual for us to have reviews span 10s of files and are very large.  They are often reviewed by a group of people and not every reviewer is viewing ever single change to every file.
One such open review we have at the moment is touching 160 files (we have pagination set at the defaults so we get 16 pages of files).
What operating system are you using? What browser?
Server and most clients on Solaris.  Browser is usually Firefox.
Please provide any additional information below.