Add the new notifications content setting preference to the list of synchronized preferences.
Add the new notifications content setting preference to the list of synchronized preferences.

BUG=48697
TEST=change notifications content settings with preference sync enabled

Review URL: http://codereview.chromium.org/2891012

git-svn-id: http://src.chromium.org/svn/trunk/src@52254 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 87cd7e1817d330fdd11e6f91a8fcc9be63cf9e23
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