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 d224471e86ff4a09869d769d38fd679c6bfb8316..bbe8503f3260e1df280cbe0da7af66e06f62d571 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -8879,6 +8879,17 @@ 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. All actions get
+    recorded by most_visited_tiles_experiment.cc, when the experiment action is

[Alexei Svitkine (slow), 2013/07/23 20:10:51]

Don't need to mention the source file or be so verbose here in general.

How about:

"Records anomalous events for the Most Visited Tile Placement experiment, where
it is not operating as expected. These are recorded during New Tab Page load
time, once for every NTP."

(assuming that matches the semantics)

[annark1, 2013/07/24 01:23:58]

Done.

+    carried out, or not carried out, as the case may be.
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.NonVisibleScreenshots">
   <summary>
     The number of screenshots that were cached for the non-visible but ranked
@@ -19305,6 +19316,18 @@ 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"/>
+</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)."/>