Adding knobs on HQP provider.

chrome/browser/history/scored_history_match.h

Index: chrome/browser/history/scored_history_match.h
diff --git a/chrome/browser/history/scored_history_match.h b/chrome/browser/history/scored_history_match.h
index 15a37e7bd73673dc4efe2ca93a5e29a06d3e8d59..83de38a1dd2a740425f8d56e82b52761c8dd111e 100644
--- a/chrome/browser/history/scored_history_match.h
+++ b/chrome/browser/history/scored_history_match.h
@@ -29,6 +29,12 @@ class ScoredHistoryMatch : public history::HistoryMatch {
   // expected to deliver (at minimum) to this class.
   static const size_t kMaxVisitsToScore;
 
+  // ScoreMaxRelevance maps from an intermediate-score to the maximum
+  // final-relevance score given to a URL for this intermediate score.
+  // This is used to store the score ranges of HQP relevance buckets.
+  // Please see GetFinalRelevancyScore() for details.
+  typedef std::pair<double, int> ScoreMaxRelevance;
+
   ScoredHistoryMatch();  // Required by STL.
 
   // Creates a new match with a raw score calculated for the history item
@@ -83,6 +89,7 @@ class ScoredHistoryMatch : public history::HistoryMatch {
 
  private:
   friend class ScoredHistoryMatchTest;
+  FRIEND_TEST_ALL_PREFIXES(ScoredHistoryMatchTest, GetFinalRelevancyScore);
   FRIEND_TEST_ALL_PREFIXES(ScoredHistoryMatchTest, ScoringBookmarks);
   FRIEND_TEST_ALL_PREFIXES(ScoredHistoryMatchTest, ScoringDiscountFrecency);
   FRIEND_TEST_ALL_PREFIXES(ScoredHistoryMatchTest, ScoringScheme);
@@ -127,10 +134,18 @@ class ScoredHistoryMatch : public history::HistoryMatch {
                             const VisitInfoVector& visits);
 
   // Combines the two component scores into a final score that's
-  // an appropriate value to use as a relevancy score.
+  // an appropriate value to use as a relevancy score. Scoring buckets are
+  // specified through |hqp_relevance_buckets|. Please see the function
+  // implementation for more details.
   static float GetFinalRelevancyScore(
       float topicality_score,
-      float frequency_score);
+      float frequency_score,
+      const std::vector<ScoreMaxRelevance>& hqp_relevance_buckets);
+
+  // Initializes the HQP experimental params,

[Mark P, 2015/02/18 00:03:32]

nit: should this be a ":" or "("/")", not a ","?  What experimental params are
not included in the below list?

[Ashok vardhan, 2015/02/18 01:11:21]

Done.

+  // |hqp_experimental_scoring_enabled_|, |topicality_threshold_| and
+  // |hqp_relevance_buckets_| specified through omnibox field trials.

[Mark P, 2015/02/18 00:03:32]

You missed this earlier comment:
By the way, this comment is wrong as written.  In particular, you end up seeing
some of these variables even if hqp_experimental_scoring is not enabled (and you
rely on these settings in the code even when experimental scoring is not
enabled).

[Ashok vardhan, 2015/02/18 01:11:21]

Done.

+  static void InitializeHQPExperimentalParams();
 
   // Sets |also_do_hup_like_scoring_|,
   // |max_assigned_score_for_non_inlineable_matches_|, |bookmark_value_|,
@@ -200,6 +215,20 @@ class ScoredHistoryMatch : public history::HistoryMatch {
   // will get demoted later in HistoryQuickProvider to non-inlineable scores.
   // Set to -1 to indicate no maximum score.
   static int max_assigned_score_for_non_inlineable_matches_;
+
+  // True, if we enable hqp experimental scoring.

[Mark P, 2015/02/18 00:03:32]

nit:
True, if we enable hqp experimental scoring.
->
True if hqp experimental scoring is enabled.

[Ashok vardhan, 2015/02/18 01:11:21]

Done.

+  static bool hqp_experimental_scoring_enabled_;
+
+  // |topicality_threshold_| is used to control the topicality scoring.
+  // If |topicality_threshold_| > 0, then URLs with topicality-score < threshold
+  // are given score 0. By default it is initalized to -1.

[Mark P, 2015/02/18 00:03:32]

"score of 0" or "topicality score of 0"?  I think you meant the former.  Yet, it
appears that topicality score of 0 doesn't translate into a final score of 0. 
(With current parameters as you point out, it gets assigned a score of 400.)

[Ashok vardhan, 2015/02/18 01:11:21]

Done.

+  static float topicality_threshold_;
+
+  // |hqp_relevance_buckets_| gives mapping from (topicality*frequency)
+  // to the final relevance scoring. Please see GetFinalRelevancyScore()
+  // for more details and scoring method.
+  static std::vector<ScoreMaxRelevance>* hqp_relevance_buckets_;
+
 };
 typedef std::vector<ScoredHistoryMatch> ScoredHistoryMatches;