[Suggestions] Remove support for a Control logging group.

components/suggestions/suggestions_service.h

Index: components/suggestions/suggestions_service.h
diff --git a/components/suggestions/suggestions_service.h b/components/suggestions/suggestions_service.h
index 4128b93fbeef9152f8df99abb3efdebee66b641f..b0d0f4c54461f1dbdd0e47af80c3c1d0e1d28d00 100644
--- a/components/suggestions/suggestions_service.h
+++ b/components/suggestions/suggestions_service.h
@@ -37,11 +37,6 @@ namespace suggestions {
 class BlacklistStore;
 class SuggestionsStore;
 
-extern const char kSuggestionsFieldTrialName[];
-extern const char kSuggestionsFieldTrialControlParam[];
-extern const char kSuggestionsFieldTrialStateEnabled[];
-extern const char kSuggestionsFieldTrialStateParam[];
-
 extern const char kSuggestionsURL[];
 extern const char kSuggestionsBlacklistURLPrefix[];
 extern const char kSuggestionsBlacklistURLParam[];
@@ -61,9 +56,6 @@ class SuggestionsService : public KeyedService, public net::URLFetcherDelegate {
       scoped_ptr<BlacklistStore> blacklist_store);
   ~SuggestionsService() override;
 
-  // Whether the user is part of a control group.
-  static bool IsControlGroup();
-
   // Request suggestions data, which will be passed to |callback|. |sync_state|
   // will influence the behavior of this function (see SyncState definition).
   //