Omnibox UI Experiments: Add feature flags for 3 URL elision experiments.

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>
 
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 extern const base::Feature kNewOmniboxAnswerTypes;
 extern const base::Feature kOmniboxEntitySuggestions;
 extern const base::Feature kOmniboxTailSuggestions;
 extern const base::Feature kEnableClipboardProvider;
 extern const base::Feature kSearchProviderWarmUpOnFocus;
 extern const base::Feature kSearchProviderContextAllowHttpsUrls;
 extern const base::Feature kZeroSuggestRedirectToChrome;
 extern const base::Feature kZeroSuggestSwapTitleAndUrl;
 extern const base::Feature kDisplayTitleForCurrentUrl;
+extern const base::Feature kUIExperimentHideSuggestionUrlPath;
+extern const base::Feature kUIExperimentHideSuggestionUrlProtocol;
+extern const base::Feature kUIExperimentHideSuggestionUrlSubdomain;
 extern const base::Feature kUIExperimentMaxAutocompleteMatches;
 extern const base::Feature kUIExperimentNarrowDropdown;
 extern const base::Feature kUIExperimentVerticalLayout;
 extern const base::Feature kUIExperimentVerticalMargin;
 }
 
 // The set of parameters customizing the HUP scoring.
 struct HUPScoringParams {
   // A set of parameters describing how to cap a given count score.  First,
   // we apply a half-life based decay of the given count and then find the
@@ skipping 496 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_