ntp_snippets: default to staging API on dev/canary

components/ntp_snippets/remote/remote_suggestions_fetcher.cc

Index: components/ntp_snippets/remote/remote_suggestions_fetcher.cc
diff --git a/components/ntp_snippets/remote/remote_suggestions_fetcher.cc b/components/ntp_snippets/remote/remote_suggestions_fetcher.cc
index 211ffa8d6a02a89927e32a6003e8896540147920..14f38f0943613005843e9690c94783c4cde916ef 100644
--- a/components/ntp_snippets/remote/remote_suggestions_fetcher.cc
+++ b/components/ntp_snippets/remote/remote_suggestions_fetcher.cc
@@ -110,12 +110,6 @@ Status FetchResultToStatus(FetchResult result) {
   return Status(StatusCode::PERMANENT_ERROR, std::string());
 }
 
-std::string GetFetchEndpoint() {
-  std::string endpoint = variations::GetVariationParamValueByFeature(
-      ntp_snippets::kArticleSuggestionsFeature, kContentSuggestionsBackend);
-  return endpoint.empty() ? kContentSuggestionsServer : endpoint;
-}
-
 bool UsesChromeContentSuggestionsAPI(const GURL& endpoint) {
   if (endpoint == kChromeReaderServer) {
     return false;
@@ -200,6 +194,16 @@ void FilterCategories(
 
 }  // namespace
 
+std::string GetFetchEndpoint(bool is_stable_or_beta_channel) {
+  std::string endpoint = variations::GetVariationParamValueByFeature(
+      ntp_snippets::kArticleSuggestionsFeature, kContentSuggestionsBackend);
+  if (endpoint.empty()) {
+    endpoint = is_stable_or_beta_channel ? kContentSuggestionsServer
+                                         : kContentSuggestionsStagingServer;
+  }
+  return endpoint;
+}
+
 CategoryInfo BuildArticleCategoryInfo(
     const base::Optional<base::string16>& title) {
   return CategoryInfo(
@@ -246,6 +250,7 @@ RemoteSuggestionsFetcher::RemoteSuggestionsFetcher(
     PrefService* pref_service,
     LanguageModel* language_model,
     const ParseJSONCallback& parse_json_callback,
+    const std::string& api_endpoint,
     const std::string& api_key,
     const UserClassifier* user_classifier)
     : OAuth2TokenService::Consumer("ntp_snippets"),
@@ -254,7 +259,7 @@ RemoteSuggestionsFetcher::RemoteSuggestionsFetcher(
       url_request_context_getter_(std::move(url_request_context_getter)),
       language_model_(language_model),
       parse_json_callback_(parse_json_callback),
-      fetch_url_(GetFetchEndpoint()),
+      fetch_url_(api_endpoint),
       fetch_api_(UsesChromeContentSuggestionsAPI(fetch_url_)
                      ? FetchAPI::CHROME_CONTENT_SUGGESTIONS_API
                      : FetchAPI::CHROME_READER_API),