NTP Zombie Code Slayer Part IV: Most Visited

      This is where things get complicated.

NTP4 had a most visited pane.  It showed your top sites.
So does the current NTP; so I'm trying to remove everything
that deals with most visited tiles on NTP4 without accidentally
breaking the same named thing on the current NTP.

Here's what used to exist that I'm trying to remove:
http://bostandjiev.com/Content/Google/chrome.jpg

Here's what currently exists that I'm trying not to break:
http://cdn.ghacks.net/wp-content/uploads/2013/04/chrome-new-tab-page.jpg

BUG=329637

Review URL: https://codereview.chromium.org/1129903008

Cr-Commit-Position: refs/heads/master@{#330910}