Changes bookmark bar drag widget to be semitransparent

Changes drag widgets such as bookmark bar items that are dragged to be semitransparent.

BUG=349154
TEST=Visual - check that a bookmark widget is semitransparent during the drag and appears over, not under the bookmark menus

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=260034

[varkha, 2014-03-27 04:54:00]

sadrul@, this is a spin-off from https://codereview.chromium.org/196213004/. Can
you please take a look? This can land before or after the rest of the bookmark
related changes. Thanks!

[sadrul, 2014-03-27 19:15:42]

This makes all drag-widgets semitransparent, right (and not just the
bookmark-bar ones)? Please update the CL subject/description.

LGTM

[varkha, 2014-03-27 20:08:29]

The CQ bit was checked by varkha@chromium.org

[commit-bot: I haz the power, 2014-03-27 20:09:41]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/varkha@chromium.org/212883011/1

[commit-bot: I haz the power, 2014-03-27 23:41:52]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-27 23:41:52]

Commit queue rejected this change because the description was changed
between the time the change entered the commit queue and the time it
was ready to commit. You can safely check the commit box again.

[varkha, 2014-03-27 23:56:45]

The CQ bit was checked by varkha@chromium.org

[commit-bot: I haz the power, 2014-03-27 23:58:24]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/varkha@chromium.org/212883011/1

[commit-bot: I haz the power, 2014-03-28 00:02:37]

Change committed as 260034