Add other variations (with ids) for NTPSnippets to chrome://flags

components/flags_ui/flags_state.h

 // Copyright 2015 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.
 
 #ifndef COMPONENTS_FLAGS_UI_FLAGS_STATE_H_
 #define COMPONENTS_FLAGS_UI_FLAGS_STATE_H_
 
 #include <stddef.h>
 
 #include <map>
 #include <set>
 #include <string>
+#include <vector>
 
 #include "base/callback_forward.h"
 #include "base/command_line.h"
 #include "base/macros.h"
 
 namespace base {
 class FeatureList;
 class ListValue;
 }
 
@@ skipping 54 matching lines @@
                               const std::string& internal_name,
                               bool enable);
   void RemoveFlagsSwitches(
       std::map<std::string, base::CommandLine::StringType>* switch_list);
   void ResetAllFlags(FlagsStorage* flags_storage);
   void Reset();
 
   // Registers variations parameter values selected for features in about:flags.
   // The selected flags are retrieved from |flags_storage|, the registered
   // variation parameters are connected to their corresponding features in
-  // |feature_list|.
-  void RegisterAllFeatureVariationParameters(FlagsStorage* flags_storage,
-                                             base::FeatureList* feature_list);
+  // |feature_list|. Returns the (possibly empty) comma separated list of
+  // additional variation ids to register in the MetricsService that come from
+  // variations selected using chrome://flags.
+  std::vector<std::string> RegisterAllFeatureVariationParameters(
+      FlagsStorage* flags_storage,
+      base::FeatureList* feature_list);
 
   // Gets the list of feature entries. Entries that are available for the
   // current platform are appended to |supported_entries|; all other entries are
   // appended to |unsupported_entries|.
   void GetFlagFeatureEntries(
       FlagsStorage* flags_storage,
       FlagAccess access,
       base::ListValue* supported_entries,
       base::ListValue* unsupported_entries,
       base::Callback<bool(const FeatureEntry&)> skip_feature_entry);
@@ skipping 76 matching lines @@
   // Map from switch name to a set of string, that keeps track which strings
   // were appended to existing (list value) switches.
   std::map<std::string, std::set<std::string>> appended_switches_;
 
   DISALLOW_COPY_AND_ASSIGN(FlagsState);
 };
 
 }  // namespace flags_ui
 
 #endif  // COMPONENTS_FLAGS_UI_FLAGS_STATE_H_