"Added X commits" discussion note has broken fade-out effect.

As seen in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11759#note_32293852

Screen_Shot_2017-06-19_at_2.00.56_PM

The fade effect starts abruptly and one pixel row of the second commit line is unaffected.

Also, when highlighted via a permalink, this fade effect sticks out even more because it does not use the blue highlighted background:

Screen_Shot_2017-06-19_at_2.05.44_PM