Use 'tile' term in MostVisitedSites.
Break out NTPTile and NTPTileSource to their own header.
Updating desktop and iOS to use ntp_tiles in one go is not going to
happen quickly. As an intermediate goal, I figured I would get them both
using NTPTile in their internals, which will make it easier to update
NewTabPage.MostVisited from MostVisitedSites on all platforms. This CL
is groundwork for that.
BUG=514752, 631990
Review-Url: https://codereview.chromium.org/2202163003
Cr-Commit-Position: refs/heads/master@{#409734}
12 files changed
