Omnibox UI Experiments: Add vertical margin variations to about:flags

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 14 matching lines @@
 namespace omnibox {
 
 extern const base::Feature kNewOmniboxAnswerTypes;
 extern const base::Feature kOmniboxEntitySuggestions;
 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 kUIExperiments;

[Mark P, 2017/05/03 18:38:59]

Double-check:
Please make sure that if we make this a feature, then we can independent
about:flags selectors that are both tied to the same feature, just set different
parameters.

[tommycli, 2017/05/03 18:49:46]

Done. I just tested this (one Feature, multiple about:flag selectors), and it
seems to work.

Admittedly, it's unprecedented.

I would say -- if indeed it doesn't work later on down the line, it wouldn't be
too disruptive in the code to split it into separate base::Feature instances.

 }
 
 // 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
   // maximum relevance score based on the decay factor or counts specified
   // in the corresponding bucket list. See comment on |buckets_| for details.
   class ScoreBuckets {
    public:
@@ skipping 443 matching lines @@
 
   // Parameter names used by the Physical Web experimental scoring experiments.
   static const char kPhysicalWebZeroSuggestBaseRelevanceParam[];
   static const char kPhysicalWebAfterTypingBaseRelevanceParam[];
 
   // 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[];
 
+  // Parameter names used by UI experiments.
+  static const char kUIExperimentsVerticalMarginParam[];
+
   // 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;
 
  private:
   friend class OmniboxFieldTrialTest;
 
   // The bundled omnibox experiment comes with a set of parameters
   // (key-value pairs).  Each key indicates a certain rule that applies in
@@ skipping 11 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_