When closing the download shelf, hide the buttons of the dangerous download
warning. Also fix the shelf closing animation.

BUG=13632
TEST=Download an exe (e.g. limewire from downloads.com), so that a "dangerous
download" message appears on the shelf. Then close the shelf. The "Yes" and "No"
buttons should be hidden, and the whole download shelf should slide down with
all items on it in place.

Original review url: http://codereview.chromium.org/159261


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@21506 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed