Add UMA stats for which icon types are shown and clicked on the NTP.
This adds two new histograms (with suffixes):
NewTabPage.TileType.<source> - Records the type of each most visited
tile that's shown on the NTP. Valid values are IconReal, IconColor,
IconDefault, ThumbnailLocal, ThumbnailServer, ThumbnailDefault.
NewTabPage.TileTypeClicked.<source> - Records the type of each most
visited tile that the user clicks on. Same values as above.
In both cases <source> can be one of "client", "server8", "popular", or
another value indicating the source of the most visited suggestions.
This CL also refactors a fair amount to support this change:
- There's a new C++/Java shared enum called MostVisitedTileType, with
the same values as the new histograms.
- Each MostVisitedItem in Java stores its tile type.
- NewTabPage.IconsGray and related histograms are now recorded in
most_visited_sites.cc alongside NewTabPage.NumberOfGrayTiles, since
these histograms are equivalent (one is for the icon NTP; one for the
thumbnail NTP)
BUG=536294
Review URL: https://codereview.chromium.org/1373983003
Cr-Commit-Position: refs/heads/master@{#351869}
12 files changed
