Close previous theme info bars when resetting to default theme

      Select and close previous theme info bars when resetting to default theme via the options dialog. As a nice side effect if one tab is showing a theme info bar and the user switches to a different theme in another tab, this change closes the previous theme info bars as well.
(landing for satish@chromium.org / http://codereview.chromium.org/1622017/show)

BUG=35607
TEST=Install a theme, and with the theme info bar visible open Preferences dialog and click 'reset to default theme' and check the info bar. (full steps given in the above bug entry)

Review URL: http://codereview.chromium.org/1650016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@45034 0039d316-1c4b-4281-b951-d872f2087c98