Add confidence to AutocompleteMatch.

chrome/browser/autocomplete/history_quick_provider.h

Index: chrome/browser/autocomplete/history_quick_provider.h
diff --git a/chrome/browser/autocomplete/history_quick_provider.h b/chrome/browser/autocomplete/history_quick_provider.h
index bd7a8244acba8d84250f0083e1d5c278ef5ed19c..7b5738f4e7b8252223d0d066650dc9e9fdf38a4e 100644
--- a/chrome/browser/autocomplete/history_quick_provider.h
+++ b/chrome/browser/autocomplete/history_quick_provider.h
@@ -52,6 +52,7 @@ class HistoryQuickProvider : public HistoryProvider {
   // the maximum possible score for the match.
   AutocompleteMatch QuickMatchToACMatch(
       const history::ScoredHistoryMatch& history_match,
+      const history::ScoredHistoryMatches& history_matches,
       bool prevent_inline_autocomplete,
       int* max_match_score);
 
@@ -64,6 +65,12 @@ class HistoryQuickProvider : public HistoryProvider {
       const history::ScoredHistoryMatch& history_match,
       int* max_match_score);
 
+  // Determines the confidence of |match| by comparing the |raw_score| to the
+  // sum of the scores of |matches|. Returns a float in the range [0, 1].
+  static float CalculateConfidence(
+      const history::ScoredHistoryMatch& match,
+      const history::ScoredHistoryMatches& matches);
+
   // Returns the index that should be used for history lookups.
   history::InMemoryURLIndex* GetIndex();