Fix regression with icon in profile delete overlay.

Make the profile icon an img instead of a background-img,
so it can have width and height. This makes the zooming
work again.

BUG=329831
TEST=Try to delete a profile with zoom setting > 100%

Review URL: https://codereview.chromium.org/103913015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241879 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241879