Limit the number of history urls indexed for omnibox suggestions.

components/omnibox/browser/omnibox_field_trial.h

 // Copyright 2014 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 COMPONENTS_OMNIBOX_BROWSER_OMNIBOX_FIELD_TRIAL_H_
 #define COMPONENTS_OMNIBOX_BROWSER_OMNIBOX_FIELD_TRIAL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 285 matching lines @@
   // 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 a default
   // value of 0.8 if no threshold is specified in the field trial.
   static float HQPExperimentalTopicalityThreshold();
 
   // ---------------------------------------------------------
+  // For experitment to limit HQP url indexing that's part of the bundled

[Mark P, 2017/05/10 17:23:09]

nit: typo (experitment)

[ssid, 2017/05/10 19:47:58]

Done.

+  // omnibox field trial.
+
+  // Returns the maximum number of history urls to index for HQP at the startup.
+  // Note: this limit is only applied at startup and more urls can be indexed
+  // during the session. Returns -1 if limit is not set by trials.
+  static int MaxNumHQPUrlsIndexedAtStartup();
+
+  // ---------------------------------------------------------
   // For the HQPFixFrequencyScoring experiment that's part of the
   // bundled omnibox field trial.
 
   // Returns true if HQP should apply the bug fix to discount the visits to
   // pages visited less than ten times.
   static bool HQPFixFewVisitsBug();
 
   // Returns true if HQP should use the weighted sum when computing frequency
   // scores.  False means to use the weighted average.  Returns false if the
   // experiment isn't active.
@@ skipping 166 matching lines @@
   static const char kHUPNewScoringVisitedCountUseDecayFactorParam[];
 
   // Parameter names used by the HQP experimental scoring experiments.
   static const char kHQPExperimentalScoringBucketsParam[];
   static const char kHQPExperimentalScoringTopicalityThresholdParam[];
 
   // Parameter names used by the Physical Web experimental scoring experiments.
   static const char kPhysicalWebZeroSuggestBaseRelevanceParam[];
   static const char kPhysicalWebAfterTypingBaseRelevanceParam[];
 
+  // Parameter name used by the experiment that limits the number of history
+  // urls indexed for suggestions.
+  static const char kMaxNumHQPUrlsIndexedAtStartupParam[];
+
   // Parameter names used by the experiment redirecting Zero Suggestion requests
   // to a service provided by the Chrome team.
   static const char kZeroSuggestRedirectToChromeServerAddressParam[];
   static const char kZeroSuggestRedirectToChromeAdditionalFieldsParam[];
 
   // 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.
   static int kDefaultMinimumTimeBetweenSuggestQueriesMs;
 
@@ skipping 16 matching lines @@
   // prioritize different wildcard contexts, see the implementation.  How to
   // interpret the value is left to the caller; this is rule-dependent.
   static std::string GetValueForRuleInContext(
       const std::string& rule,
       metrics::OmniboxEventProto::PageClassification page_classification);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(OmniboxFieldTrial);
 };
 
 #endif  // COMPONENTS_OMNIBOX_BROWSER_OMNIBOX_FIELD_TRIAL_H_