Fix one more case where we could theoretically intall an extension without a prompt. See also r36501.
Fix one more case where we could theoretically intall an extension
without a prompt. See also r36501.

TBR=erikkay@chromium.org

git-svn-id: http://src.chromium.org/svn/trunk/src@36503 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 026aa0da78dfe949223999dfa930fe9401d46006
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