Omnibox UI Experiments: Add flag to change max autocomplete matches.

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 fd96b33c741c7d9c50cf3e70b311f81e0beb8307..579cb81c659c0b759756424e6b73774134ec48a9 100644
--- a/components/omnibox/browser/omnibox_field_trial.h
+++ b/components/omnibox/browser/omnibox_field_trial.h
@@ -32,6 +32,7 @@ extern const base::Feature kSearchProviderContextAllowHttpsUrls;
 extern const base::Feature kZeroSuggestRedirectToChrome;
 extern const base::Feature kZeroSuggestSwapTitleAndUrl;
 extern const base::Feature kDisplayTitleForCurrentUrl;
+extern const base::Feature kUIExperimentMaxAutocompleteMatches;
 extern const base::Feature kUIExperimentVerticalMargin;
 }
 
@@ -497,6 +498,7 @@ class OmniboxFieldTrial {
   static const char kZeroSuggestRedirectToChromeAdditionalFieldsParam[];
 
   // Parameter names used by UI experiments.
+  static const char kUIMaxAutocompleteMatchesParam[];
   static const char kUIVerticalMarginParam[];
 
   // The amount of time to wait before sending a new suggest request after the