Limit the number of history urls indexed for omnibox suggestions.

components/omnibox/browser/omnibox_field_trial.h

Index: components/omnibox/browser/omnibox_field_trial.h
diff --git a/components/omnibox/browser/omnibox_field_trial.h b/components/omnibox/browser/omnibox_field_trial.h
index 82185aaf3dec36da126ca7e3e804061fabc24a43..da49a7e67503403449f639060c5bf03ae021e050 100644
--- a/components/omnibox/browser/omnibox_field_trial.h
+++ b/components/omnibox/browser/omnibox_field_trial.h
@@ -302,6 +302,15 @@ class OmniboxFieldTrial {
   // value of 0.8 if no threshold is specified in the field trial.
   static float HQPExperimentalTopicalityThreshold();
 
+  // ---------------------------------------------------------
+  // For experiment to limit HQP url indexing that's part of the bundled
+  // 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.
@@ -485,6 +494,11 @@ class OmniboxFieldTrial {
   static const char kHQPExperimentalScoringBucketsParam[];
   static const char kHQPExperimentalScoringTopicalityThresholdParam[];
 
+  // Parameter names used by the experiment that limits the number of history
+  // urls indexed for suggestions.
+  static const char kMaxNumHQPUrlsIndexedAtStartupOnLowEndDevicesParam[];
+  static const char kMaxNumHQPUrlsIndexedAtStartupOnNonLowEndDevicesParam[];
+
   // Parameter names used by the Physical Web experimental scoring experiments.
   static const char kPhysicalWebZeroSuggestBaseRelevanceParam[];
   static const char kPhysicalWebAfterTypingBaseRelevanceParam[];