Don't demote top match for certain match types.

chrome/browser/autocomplete/autocomplete_result.cc

Index: chrome/browser/autocomplete/autocomplete_result.cc
diff --git a/chrome/browser/autocomplete/autocomplete_result.cc b/chrome/browser/autocomplete/autocomplete_result.cc
index 0c01b3923344778c50e930e693230cfa507aa19c..8430da06689aaddd747c5acb4200250814930e0d 100644
--- a/chrome/browser/autocomplete/autocomplete_result.cc
+++ b/chrome/browser/autocomplete/autocomplete_result.cc
@@ -47,7 +47,7 @@ int CompareWithDemoteByType::GetDemotedRelevance(
     const AutocompleteMatch& match) {
   OmniboxFieldTrial::DemotionMultipliers::const_iterator demotion_it =
       demotions_.find(match.type);
-  return (demotion_it == demotions_.end()) ?
+  return (demotion_it == demotions_.end() || !match.demoteable) ?
       match.relevance : (match.relevance * demotion_it->second);
 }
 
@@ -154,6 +154,16 @@ void AutocompleteResult::SortAndCull(const AutocompleteInput& input,
                              &AutocompleteMatch::DestinationsEqual),
                  matches_.end());
 
+  // Don't demote the top match if applicable.
+  OmniboxFieldTrial::UndemotableTopMatchTypes undemotable_top_types;
+  OmniboxFieldTrial::GetUndemotableTopTypes(input.current_page_classification(),
+                                            &undemotable_top_types);
+  if (!matches_.empty() &&
+      undemotable_top_types.find(matches_.begin()->type) !=
+      undemotable_top_types.end()) {
+    matches_.begin()->demoteable = false;

[Peter Kasting, 2013/10/31 23:27:59]

Is this basically only used by code called from the block below?

Because if so, rather than add a new member to AutocompleteMatch, perhaps we
could simply pull off the front match here, run the sort/demote on the rest, and
then put the front match back.

[H Fung, 2013/11/01 23:42:56]

Yes, thanks.  I've made the change.

+  }
+
   // Sort and trim to the most relevant kMaxMatches matches.
   size_t max_num_matches = std::min(kMaxMatches, matches_.size());
   CompareWithDemoteByType comparing_object(input.current_page_classification());