Cleanup: Move PaintVerticalDivider() into bookmark_bar_view.cc.

Cleanup: Move PaintVerticalDivider() into bookmark_bar_view.cc.

Actually it does not have to do much with DetachableToolbarView.

It is used by BookmarkBarView to draw a button separator in the left
side of "Other bookmarks" folder. The "Other bookmarks" only appears
when you actually have bookmarks on it. So to separate it from the rest
of the Bookmarks bar nodes, a separator is drawn.

Screenshot: http://imgur.com/nW38lEy

BUG=None
TEST=open chrome, bookmark something in the "Other bookmarks" folder,
make sure you have "Bookmarks bar" shown, then make sure the separator
is there. No regressions observed.
R=sky@chromium.org

Committed: https://crrev.com/39f40c222c49aab7b49c97c14eec019cd1d4ac49
Cr-Commit-Position: refs/heads/master@{#308371}

[tfarina, 2014-12-14 17:33:07]

PTAL

[sky, 2014-12-15 17:00:24]

LGTM

[tfarina, 2014-12-15 17:09:40]

The CQ bit was checked by tfarina@chromium.org

[commit-bot: I haz the power, 2014-12-15 17:10:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/798283002/1

[commit-bot: I haz the power, 2014-12-15 18:05:56]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-15 18:06:55]

Patchset 1 (id:??) landed as
https://crrev.com/39f40c222c49aab7b49c97c14eec019cd1d4ac49
Cr-Commit-Position: refs/heads/master@{#308371}