In a Pull Request, the last lines of Diff may be hidden

Issue Summary

In the Diff view of a Pull Request, the last lines may not be shown.
When it happens, the reviewer may approve and merge PR without seeing all the changes in the code.

Steps to Reproduce

1. Create a Pull Request where 200 lines have been added to a file
   (with 160 lines added, the problem did not occur)
2. Open the Pull Request and switch to the Diff view
3. Scroll all the way down and note that all 200 added lines are shown
   
4. Click on one of the green lines, then use Ctrl+F (or Command+F) to display the Find: field
5. Type some random search string in the Find field (e.g., Test) and click the Next match and Previous match buttons a few times
6. Scroll all the way down and note that a few last lines are no longer shown
   
   (in case the issue does not immediately occur, scroll up and down a few more times) 

Expected Results

Each time you scroll all the way down, the last line of Diff should be visible (in this case, line number 200)

Actual Results

The last line shown may not always be #200, but rather #197 or #194 etc.
As a reviewer, you are now missing a number of changes included in this Pull Request.

Workaround

Resizing the browser window, or re-entering the Pull Request, should show the entire Diff again.
However, the reviewers may not know that they are missing a number of last lines.