Small fixes for url_index_private_data.cc

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 1043e5631c3993d0e32a18ba3388cdb14f3014aa..c63445e1a09872b80777e8da94bcb0019c2611b9 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -40749,6 +40749,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Omnibox.HistoryQuickHistoryIDSetFromWords" units="ms">
+  <owner>mpearson@chromium.org</owner>
+  <summary>
+    Times URLIndexPrivateData::HistoryIDSetFromWords(), which is called by the
+    omnibox's HistoryQuick provider.
+    URLIndexPrivateData::HistoryIDSetFromWords() can be called multiple times
+    per keystroke due to, for example, the cursor being in the middle of the
+    input string or SearchProvider's calls to Classify().
+  </summary>
+</histogram>
+
 <histogram name="Omnibox.InputType" enum="OmniboxInputType">
   <owner>mpearson@chromium.org</owner>
   <summary>