Field trial removing tiles from NTP if URL is already open - for 1993 clients

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 af22ae60b483b5633f64e1f59dd93590a2aa8a7c..ca49713a6f014b285d8feb0c8a879ec72d9fbfbe 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -7975,6 +7975,15 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="NewTabPage.MostVisitedTilePlacementExperiment"
+    enum="NtpTileExperimentActions">
+  <summary>
+    Histogram of actions carried out by Most Visited Tile Placement experiment.
+    The reason for this histogram is to identify the cases where the experiment
+    could not operate as expected, and the reason for it.
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.NonVisibleScreenshots">
   <summary>
     The number of screenshots that were cached for the non-visible but ranked
@@ -18141,6 +18150,19 @@ other types of suffix sets.
   <int value="2" label="NTP Promo link clicked"/>
 </enum>
 
+<enum name="NtpTileExperimentActions" type="int">
+  <summary>
+    The types of actions performed by the Most Visited Tile Placement
+    experiment, used to identify the cases where the experiment could not
+    operate as expected, and the reason for it.
+  </summary>
+  <int value="0" label="Removed URL that was already open in browser"/>
+  <int value="1" label="Didn't remove URL, too few suggestions in MV"/>
+  <int value="2" label="Too few URLs, didn't flip tiles 1 and 8"/>
+  <int value="3" label="Too few URLs, didn't flip tiles 1 and 4"/>
+  <int value="4" label="No URL, couldn't flip any tiles"/>
+</enum>
+
 <enum name="OfflineStatus" type="int">
   <int value="0" label="Fresh data load from Cache"/>
   <int value="1" label="Successful network request (validation or fetch)."/>