tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 5048829583dbd6588749d981f25420e9a65bc504..2986ee553c4671e363ce542ecb6c05fef075e9fd 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -39795,8 +39795,8 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <owner>justincohen@chromium.org</owner>
   <owner>newt@chromium.org</owner>
   <summary>
-    Histogram for user clicks of the most visited thumbnails. The value is equal
-    to the index of the thumbnail.
+    Histogram for user clicks of the most visited tile. The value is equal to
+    the index of the tile.
   </summary>
 </histogram>
 
@@ -39814,6 +39814,36 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NewTabPage.MostVisitedClickIcon.Color"
+    enum="MostVisitedTileIndex">
+  <owner>mastiz@chromium.org</owner>
+  <summary>
+    Clicks on the various most visited tiles using a fallback color (as opposed
+    to having an icon, or simply being gray). The value is equal to the index of
+    the tile.
+  </summary>
+</histogram>
+
+<histogram name="NewTabPage.MostVisitedClickIcon.Gray"
+    enum="MostVisitedTileIndex">
+  <owner>mastiz@chromium.org</owner>
+  <summary>
+    Clicks on the various most visited tiles displayed as gray (as opposed to
+    having an icon, or a fallback color). The value is equal to the index of the
+    tile.
+  </summary>
+</histogram>
+
+<histogram name="NewTabPage.MostVisitedClickIcon.Real"

[Alexei Svitkine (slow), 2017/02/07 16:03:17]

Please use histogram_suffixes construct to void duplication here.

[mastiz, 2017/02/09 08:23:37]

Done.

This made me thing whether we should actually use the already existing
Histograms (SuggestionsImpression, MostVisisted), since the ones introduced here
are breakdowns per icon appearance. However, another breakdown/suffix already
exists for those (for the actual data-source that provides the suggestion),
which could potentially create (a) confusion and (b) naming collisions.

Nevertheless, I went ahead with this idea. Is this a common way to express
multiple breakdowns per metric?

[Alexei Svitkine (slow), 2017/02/09 16:34:54]

Yep, this is the suggested way when doing this sort of thing.

+    enum="MostVisitedTileIndex">
+  <owner>mastiz@chromium.org</owner>
+  <summary>
+    Clicks on the various most visited tiles displayed with the site's icon (as
+    opposed using a fallback color or just gray). The value is equal to the
+    index of the tile.
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.MostVisitedScheme" enum="NtpMostVisitedScheme">
   <obsolete>
     Deprecated 2016-05.
@@ -40556,6 +40586,36 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NewTabPage.SuggestionsImpressionIcon.Color"
+    enum="MostVisitedTileIndex">
+  <owner>mastiz@chromium.org</owner>
+  <summary>
+    Histogram for impressions on the various most visited tiles using a fallback
+    color (as opposed to having an icon, or simply being gray). The value is
+    equal to the index of the tile.
+  </summary>
+</histogram>
+
+<histogram name="NewTabPage.SuggestionsImpressionIcon.Gray"
+    enum="MostVisitedTileIndex">
+  <owner>mastiz@chromium.org</owner>
+  <summary>
+    Histogram for impressions on the various most visited tiles displayed as
+    gray (as opposed to having an icon, or a fallback color). The value is equal
+    to the index of the tile.
+  </summary>
+</histogram>
+
+<histogram name="NewTabPage.SuggestionsImpressionIcon.Real"
+    enum="MostVisitedTileIndex">
+  <owner>mastiz@chromium.org</owner>
+  <summary>
+    Histogram for impressions on the various most visited tiles displayed with
+    the site's icon (as opposed using a fallback color or just gray). The value
+    is equal to the index of the tile.
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.SuggestionsType" enum="NtpSuggestionsType">
   <obsolete>
     Deprecated 2016-07.