Fix a memory leak found by Valgrind.
Fix a memory leak found by Valgrind.

See https://developer.mozilla.org/en/NPN_GetProperty for doc
on proper use of NPN_GetProperty.

BUG=9515

Review URL: http://codereview.chromium.org/155730

git-svn-id: http://src.chromium.org/svn/trunk/src@21027 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 532f45cf2d15935ee6094d3956569a18ca5daa04
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