Don't query ZeroSuggest or show MostVisited on InstantExtended NTP.

BUG=305366

Review URL: https://codereview.chromium.org/26129007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228560 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228560