downloads: remove focus row background color.

downloads: remove focus row background color.

The DOM is currently not set up well for a background color, making this
really ugly.

I'll get this working in the future, but it'll involve hacking up the
HTML structure a bit.

BUG=458483
R=groby@chromium.org
TEST=visual

Committed: https://crrev.com/934dcb177acc5f7d2b2b8d3475abcb5d51c48257
Cr-Commit-Position: refs/heads/master@{#316304}

[groby-ooo-7-16, 2015-02-13 20:10:15]

lgtm

[Dan Beam, 2015-02-13 20:11:21]

The CQ bit was checked by dbeam@chromium.org

[commit-bot: I haz the power, 2015-02-13 20:12:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/921273002/1

[commit-bot: I haz the power, 2015-02-13 22:11:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-13 22:12:07]

Patchset 1 (id:??) landed as
https://crrev.com/934dcb177acc5f7d2b2b8d3475abcb5d51c48257
Cr-Commit-Position: refs/heads/master@{#316304}