Shown lines for comments in MR code Review are not the selected ones but always 15

Summary

There's a visualization issue when I comment on some specific lines in MRs: I see the correct number of lines the comment refers to below the code (in the picture, +281 to +282) but the box showing code shows 15 lines always (+267 to +282).

Steps to reproduce

Create an MR, comment on 2 lines, see 15 lines showing.

Example Project

What is the current bug behavior?

15 lines of code are shown always in the code box.

What is the expected correct behavior?

Code box shows only lines the comment refers to.

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes