Don't close the last tab when launching a panel app
Don't close the last tab when launching a panel app

BUG=59998
TEST=Launch a panel application from the new tab page when no other tabs are open. The tab shouldn't close.

Review URL: http://codereview.chromium.org/3995001

git-svn-id: http://src.chromium.org/svn/trunk/src@63272 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: e7d13af9fea0b95997be63dd85cc1d87a521410e
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