Adding performance tests for HQP that represent importance of optimising HistoryItemsForTerms method

components/omnibox/browser/url_index_private_data.cc

Index: components/omnibox/browser/url_index_private_data.cc
diff --git a/components/omnibox/browser/url_index_private_data.cc b/components/omnibox/browser/url_index_private_data.cc
index 54123a335ca874ae527c5babe079cf242c08fc5e..948408c1a68d62392d06b5fb27ba438573a79460 100644
--- a/components/omnibox/browser/url_index_private_data.cc
+++ b/components/omnibox/browser/url_index_private_data.cc
@@ -522,6 +522,7 @@ URLIndexPrivateData::~URLIndexPrivateData() {}
 
 HistoryIDSet URLIndexPrivateData::HistoryIDSetFromWords(
     const String16Vector& unsorted_words) {
+  SCOPED_UMA_HISTOGRAM_TIMER("Omnibox.HistoryIDSetFromWords");
   // Break the terms down into individual terms (words), get the candidate
   // set for each term, and intersect each to get a final candidate list.
   // Note that a single 'term' from the user's perspective might be