Allow overriding variation parameter via chrome://flags.

chrome/browser/about_flags.cc

 // Copyright (c) 2012 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 "chrome/browser/about_flags.h"
 
 #include <iterator>
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 1994 matching lines @@
                             base::CommandLine* command_line,
                             flags_ui::SentinelsMode sentinels) {
   if (command_line->HasSwitch(switches::kNoExperiments))
     return;
 
   FlagsStateSingleton::GetFlagsState()->ConvertFlagsToSwitches(
       flags_storage, command_line, sentinels, switches::kEnableFeatures,
       switches::kDisableFeatures);
 }
 
+void RegisterFeatureVariationParameters(flags_ui::FlagsStorage* flags_storage) {
+  FlagsStateSingleton::GetFlagsState()->RegisterFeatureVariationParameters(
+      flags_storage);
+}
+
 bool AreSwitchesIdenticalToCurrentCommandLine(
     const base::CommandLine& new_cmdline,
     const base::CommandLine& active_cmdline,
     std::set<base::CommandLine::StringType>* out_difference) {
   const char* extra_flag_sentinel_begin_flag_name = nullptr;
   const char* extra_flag_sentinel_end_flag_name = nullptr;
 #if defined(OS_CHROMEOS)
   // Put the flags between --policy-switches--begin and --policy-switches-end on
   // ChromeOS.
   extra_flag_sentinel_begin_flag_name =
@@ skipping 85 matching lines @@
 const base::HistogramBase::Sample kBadSwitchFormatHistogramId = 0;
 
 const FeatureEntry* GetFeatureEntries(size_t* count) {
   *count = arraysize(kFeatureEntries);
   return kFeatureEntries;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags