[NTP::SectionOrder] Track category index after it has been moved up.

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 42031f55a20a6ef91874660c9840017ce2d5b85f..6aac7a9141dd6f45c053561cc6e93bc369312662 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -39226,6 +39226,19 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NewTabPage.ContentSuggestions.MovedUpCategoryNewIndex"
+    units="index">
+  <owner>vitaliii@chromium.org</owner>
+  <summary>
+    Android: The new index of a category on the NTP after it has been moved up
+    due to a click. The index of a category, which has been overtaken, is not
+    recorded here. This tracked index can be different from the position
+    observed by the user, e.g. empty categories are not shown. This metric
+    ignores all other order changes (e.g. dismissing a category or clearing
+    history).
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.ContentSuggestions.Notifications.Actions"
     enum="ContentSuggestionsNotificationsAction">
   <owner>sfiera@chromium.org</owner>