Fix 33130 by checking whether the tab is closed when closing login propmt
Fix 33130 by checking whether the tab is closed when
closing login propmt

BUG=33130 
TEST=existing test passes

Review URL: http://codereview.chromium.org/576010

git-svn-id: http://src.chromium.org/svn/trunk/src@38165 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 8216690e20853ea545666883bbc596c77f8351d9
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser