Merge request diff in mobile

Raising this issue because of this one gitlab-ce#25930

In mobile, the Changes tab in the Merge Request view is not usable. When we have comments, the text overflows, most of the time making it impossible to read.

I am not 100% sure if reviewing a MR in a mobile is a use case, so I am adding gitlab-ce~2024187 label as well.

Side by Side: Screen_Shot_2016-12-22_at_18.48.54

Inline: Screen_Shot_2016-12-22_at_18.49.14

//cc @awhildy @sarahod

Edited by 🤖 GitLab Bot 🤖