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 1903 matching lines @@
     {"enable-font-cache-scaling",
      IDS_FLAGS_FONT_CACHE_SCALING_NAME,
      IDS_FLAGS_FONT_CACHE_SCALING_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kFontCacheScaling)},
 #if defined(OS_ANDROID)
     {"enable-vr-shell",
      IDS_FLAGS_ENABLE_VR_SHELL_NAME,
      IDS_FLAGS_ENABLE_VR_SHELL_DESCRIPTION, kOsAndroid,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableVrShell,
                                switches::kDisableVrShell)},
 #endif

[Alexei Svitkine (slow), 2016/06/16 09:40:57]

Seems like you both rebased and also addressed comments in the same patchset.
It's not the end of the world, but it makes it harder to review changes between
patchsets, so in the future it's a good idea to rebase, upload your patch set
and then address comments after that in a separate patchset.

[jkrcal, 2016/06/16 14:49:17]

You are right, I am sorry about it!

 
     {"enable-weak-memorycache",
      IDS_FLAGS_ENABLE_WEAK_MEMORYCACHE_NAME,
      IDS_FLAGS_ENABLE_WEAK_MEMORYCACHE_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kWeakMemoryCache)},
     // NOTE: Adding new command-line switches requires adding corresponding
     // entries to enum "LoginCustomFlags" in histograms.xml. See note in
     // histograms.xml and don't forget to run AboutFlagsHistogramTest unit test.
 };
 
@@ skipping 79 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 RegisterAllFeatureVariationParameters(
+    flags_ui::FlagsStorage* flags_storage) {
+  FlagsStateSingleton::GetFlagsState()->RegisterAllFeatureVariationParameters(
+      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