Track age and score of snippets that are clicked (along with position).

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 391242f244846eb38985d9e8a0799f8e83157fcf..686b7fbbb14035dd6e269c995a08376c43654aa4 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -33668,6 +33668,26 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NewTabPage.Snippets.CardClickedAge" units="min">

[Alexei Svitkine (slow), 2016/05/24 17:21:56]

Nit: minutes

+  <owner>jkrcal@chromium.org</owner>
+  <summary>
+    Android: The age of the snippets card on the NTP, that is clicked through to
+    the host website of the content. The age is measured from the moment the
+    content has been published. In each &quot;_x_y&quot; suffix of the
+    histogram, only snippets on positions \gt;=x and \lt;=y are tracked.
+  </summary>
+</histogram>
+
+<histogram name="NewTabPage.Snippets.CardClickedScore" units="score">
+  <owner>jkrcal@chromium.org</owner>
+  <summary>
+    Android: The score of the snippets card on the NTP, that is clicked through
+    to the host website of the content. The recorded score is from the moment
+    the snippet was fetched, it could have changed since. In each &quot;_x&quot;
+    suffix  of the histogram, only snippets on positions \lt;=x are tracked.
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.Snippets.CardExpanded">
   <owner>knn@chromium.org</owner>
   <summary>
@@ -94802,6 +94822,15 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="NaCl.Perf.Size.PNaClTranslatedNexe"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="PositionVariants">
+  <suffix name="0_0" label="Only snippets on position 0"/>
+  <suffix name="1_2" label="Only snippets on position 1-2"/>
+  <suffix name="3_4" label="Only snippets on position 3-4"/>
+  <suffix name="5_9" label="Only snippets on position 5-9"/>
+  <affected-histogram name="NewTabPage.Snippets.CardClickedAge"/>
+  <affected-histogram name="NewTabPage.Snippets.CardClickedScore"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="PpapiPluginName">
   <suffix name="libpepflashplayer.so" label="Flash player on Linux or Cros"/>
   <suffix name="libwidevinecdmadapter.so"