Bug 1659603

Description of problem:

Problem appeared after the upgrade to 5.0 as far as I understand.
On previous release when someone clicks on the attachment, then the following could happen:
1) If it is a patch, then it opens in browser and content of the patch is shown (without fancy colours and with correct indentation). Content of the patch was shown in plain text mode.
2) If the file is a plain text file, then it opens in browser and can be observed.

With a new version the behaviour is different:
1) If it is a patch file, then browser suggests to download it (and doesn't open it). When someone clicks on "Diff", then the behaviour is like this:
by default it shows the diff in fancy colours and shows by default side-by-side. While the expected that by default it should be line-by-line (like in the previous version).

The most important bug here is that indentation is broken. In previous version plain text was shown with correct indentation while in the new version of Bugzilla it looks like formats the output and breaks the correct indentation.

2) When it is a plain text attachments it suggests to download it.

Examples: 1653437, 1576008

Version-Release number of selected component (if applicable):

New release 5.0 (as far as I understood).

How reproducible:

Always.

Steps to Reproduce:
1. Perform described actions.

Actual results:

Described above.

Expected results:

It is expected that old behavior remains -- like viewing attachments in the browser in good old plain text mode with correct indentation.
Instead new behaviour breaks indentation and doesn't allow to view attachments in plain text mode.
Also i wasn't able to find option in preferences to make line-by-line view default and any other options to make bugzilla behave in an old way.