Add base::FeatureParam<> struct

components/ntp_snippets/remote/remote_suggestions_fetcher.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/remote/remote_suggestions_fetcher.h"
 
 #include <cstdlib>
 #include <utility>
 
 #include "base/files/file_path.h"
@@ skipping 32 matching lines @@
 using internal::JsonRequest;
 using internal::FetchResult;
 
 namespace {
 
 const char kContentSuggestionsApiScope[] =
     "https://www.googleapis.com/auth/chrome-content-suggestions";
 const char kSnippetsServerNonAuthorizedFormat[] = "%s?key=%s";
 const char kAuthorizationRequestHeaderFormat[] = "Bearer %s";
 
-// Variation parameter for chrome-content-suggestions backend.
-const char kContentSuggestionsBackend[] = "content_suggestions_backend";
+constexpr base::FeatureParam<std::string> kContentSuggestionsBackend{
+    &kArticleSuggestionsFeature, "content_suggestions_backend",
+    kContentSuggestionsServer};
 
 const int kFetchTimeHistogramResolution = 5;
 
 std::string FetchResultToString(FetchResult result) {
   switch (result) {
     case FetchResult::SUCCESS:
       return "OK";
     case FetchResult::URL_REQUEST_STATUS_ERROR:
       return "URLRequestStatus error";
     case FetchResult::HTTP_ERROR:
@@ skipping 101 matching lines @@
     return;
   }
   RemoteSuggestionsFetcher::FetchedCategory category = std::move(*category_it);
   categories->clear();
   categories->push_back(std::move(category));
 }
 
 }  // namespace
 
 GURL GetFetchEndpoint(version_info::Channel channel) {
-  std::string endpoint = variations::GetVariationParamValueByFeature(
-      ntp_snippets::kArticleSuggestionsFeature, kContentSuggestionsBackend);
+  std::string endpoint = kContentSuggestionsBackend.Get();
   if (!endpoint.empty()) {
     return GURL{endpoint};
   }
 
   switch (channel) {
     case version_info::Channel::STABLE:
     case version_info::Channel::BETA:
       return GURL{kContentSuggestionsServer};
 
     case version_info::Channel::DEV:
@@ skipping 302 matching lines @@
           category, BuildRemoteCategoryInfo(base::UTF8ToUTF16(utf8_title),
                                             allow_fetching_more_results)));
     }
     categories->back().suggestions = std::move(suggestions);
   }
 
   return true;
 }
 
 }  // namespace ntp_snippets