Adding knobs on HQP provider.

components/omnibox/omnibox_field_trial.h

Index: components/omnibox/omnibox_field_trial.h
diff --git a/components/omnibox/omnibox_field_trial.h b/components/omnibox/omnibox_field_trial.h
index 5a439e2f384a6dd62e2d1a5ceba56938d58b8325..36c77221156c8a395fb7d06d4e7230e5b9cd302b 100644
--- a/components/omnibox/omnibox_field_trial.h
+++ b/components/omnibox/omnibox_field_trial.h
@@ -270,6 +270,25 @@ class OmniboxFieldTrial {
                                         int* polling_delay_ms);
 
   // ---------------------------------------------------------
+  // For HQP scoring related experiments to control the topicality and scoring
+  // ranges of relevancy scores.
+
+  // Returns true if HQP experimental scoring is enabled. Returns false if
+  // |kHQPExperimentalScoringEnabledParam| is not defined.

[Mark P, 2015/02/14 01:27:14]

This last sentence is wrong.  This variable is a static member variable and is
always defined/initialized.  You mean something like "Returns false if the
appropriate parameter is not specified in the field trial."

analogous both places below (something like)
Returns false if experimental scoring is not enabled or if the appropriate
parameter is not specified in the field trial.

[Ashok vardhan, 2015/02/17 01:23:53]

Acknowledged.

+  static bool HQPExperimentalScoringEnabled();
+
+  // Returns the scoring buckets for HQP experiments. Returns empty string
+  // in case |kHQPExperimentalScoringBucketsParam| is not defined. Scoring
+  // buckets are stored in string form giving mapping from (topicality_score,
+  // frequency_score) to final relevance score. Please see GetRelevancyScore()
+  // under chrome/browser/history::ScoredHistoryMatch for details.
+  static std::string HQPExperimentalScoringBuckets();
+
+  // Returns the topicality threshold for HQP experiments. Returns -1 if
+  // |kHQPExperimentalScoringTopicalityThresholdParam| is not defined.
+  static float HQPExperimentalTopicalityThreshold();
+
+  // ---------------------------------------------------------
   // Exposed publicly for the sake of unittests.
   static const char kBundledExperimentFieldTrialName[];
   // Rule names used by the bundled experiment.
@@ -298,6 +317,11 @@ class OmniboxFieldTrial {
   static const char kHUPNewScoringVisitedCountHalfLifeTimeParam[];
   static const char kHUPNewScoringVisitedCountScoreBucketsParam[];
 
+  // Parameter names used by the HQP experimental scoring experiments.
+  static const char kHQPExperimentalScoringEnabledParam[];
+  static const char kHQPExperimentalScoringBucketsParam[];
+  static const char kHQPExperimentalScoringTopicalityThresholdParam[];
+
   // The amount of time to wait before sending a new suggest request after the
   // previous one unless overridden by a field trial parameter.
   // Non-const because some unittests modify this value.