Add confidence to AutocompleteMatch.

chrome/browser/autocomplete/history_quick_provider.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_AUTOCOMPLETE_HISTORY_QUICK_PROVIDER_H_
 #define CHROME_BROWSER_AUTOCOMPLETE_HISTORY_QUICK_PROVIDER_H_
 #pragma once
 
 #include <string>
 
@@ skipping 31 matching lines @@
 
  private:
   friend class HistoryQuickProviderTest;
   FRIEND_TEST_ALL_PREFIXES(HistoryQuickProviderTest, Spans);
   FRIEND_TEST_ALL_PREFIXES(HistoryQuickProviderTest, Relevance);
 
   // The initial maximum allowable score for a match which cannot be inlined.
   static const int kMaxNonInliningScore;
 
   // Creates an AutocompleteMatch from |history_match|. |max_match_score| gives
-  // the maximum possible score for the match.
+  // the maximum possible score for the match. |history_matches| is the full set
+  // of matches to compare each match to when calculating confidence.
   AutocompleteMatch QuickMatchToACMatch(
       const history::ScoredHistoryMatch& history_match,
+      const history::ScoredHistoryMatches& history_matches,
       bool prevent_inline_autocomplete,
       int* max_match_score);
 
   // Determines the relevance score of |history_match|. The maximum allowed
   // score for the match is passed in |max_match_score|. The |max_match_score|
   // is always set to the resulting score minus 1 whenever the match's score
   // has to be limited or is <= to |max_match_score|. This function should be
   // called in a loop with each match in decreasing order of raw score.
   static int CalculateRelevance(
       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();
 
   // Fill and return an ACMatchClassifications structure given the term
   // matches (|matches|) to highlight where terms were found.
   static ACMatchClassifications SpansFromTermMatch(
       const history::TermMatches& matches,
       size_t text_length,
       bool is_url);
 
   // Only for use in unittests.  Takes ownership of |index|.
   void SetIndexForTesting(history::InMemoryURLIndex* index);
   AutocompleteInput autocomplete_input_;
   std::string languages_;
 
   // Only used for testing.
   scoped_ptr<history::InMemoryURLIndex> index_for_testing_;
 };
 
 #endif  // CHROME_BROWSER_AUTOCOMPLETE_HISTORY_QUICK_PROVIDER_H_