Drop ntp_snippets::kStudyName in chrome://flags

components/ntp_snippets/category_rankers/click_based_category_ranker_unittest.cc

 // Copyright 2016 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.
 
 #include "components/ntp_snippets/category_rankers/click_based_category_ranker.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 66 matching lines @@
       ranker()->OnSuggestionOpened(category);
     }
   }
 
   void NotifyOnCategoryDismissed(Category category) {
     ranker()->OnCategoryDismissed(category);
   }
 
   void SetDismissedCategoryPenaltyVariationParam(int value) {
     variation_params_manager_.SetVariationParamsWithFeatureAssociations(
-        ntp_snippets::kStudyName,
+        kCategoryRanker.name,
         {{"click_based_category_ranker-dismissed_category_penalty",
           base::IntToString(value)}},
         {kCategoryRanker.name});
   }
 
   void SetPromotedCategoryVariationParam(int value) {
     variation_params_manager_.SetVariationParamsWithFeatureAssociations(
-        ntp_snippets::kStudyName,
+        kCategoryRanker.name,
         {{"click_based_category_ranker-promoted_category",
           base::IntToString(value)}},
         {kCategoryRanker.name});
   }
 
   ClickBasedCategoryRanker* ranker() { return ranker_.get(); }
 
  private:
   std::unique_ptr<TestingPrefServiceSimple> pref_service_;
   int unused_remote_category_id_;
@@ skipping 634 matching lines @@
   SetPromotedCategoryVariationParam(second.id());
   ResetRanker(base::MakeUnique<base::DefaultClock>());
 
   ASSERT_FALSE(CompareCategories(first, second));
 
   EXPECT_THAT(histogram_tester.GetAllSamples(kHistogramMovedUpCategoryNewIndex),
               IsEmpty());
 }
 
 }  // namespace ntp_snippets