Componentize internal class FlagsState in flags_ui component.

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>
 
+#include "base/bind.h"
+#include "base/callback.h"
 #include "base/command_line.h"
 #include "base/feature_list.h"
 #include "base/memory/singleton.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "cc/base/switches.h"
 #include "chrome/common/channel_info.h"
 #include "chrome/common/chrome_content_client.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/grit/chromium_strings.h"
 #include "chrome/grit/generated_resources.h"
 #include "chrome/grit/google_chrome_strings.h"
 #include "components/autofill/core/common/autofill_switches.h"
 #include "components/browser_sync/common/browser_sync_switches.h"
 #include "components/cloud_devices/common/cloud_devices_switches.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_switches.h"
 #include "components/dom_distiller/core/dom_distiller_switches.h"
 #include "components/enhanced_bookmarks/enhanced_bookmark_switches.h"
 #include "components/flags_ui/feature_entry_macros.h"
 #include "components/flags_ui/flags_storage.h"
+#include "components/flags_ui/flags_ui_switches.h"
 #include "components/metrics/metrics_hashes.h"
 #include "components/nacl/common/nacl_switches.h"
 #include "components/offline_pages/offline_page_switches.h"
 #include "components/omnibox/browser/omnibox_switches.h"
 #include "components/password_manager/core/common/password_manager_switches.h"
 #include "components/plugins/common/plugins_switches.h"
 #include "components/proximity_auth/switches.h"
 #include "components/search/search_switches.h"
 #include "components/signin/core/common/signin_switches.h"
 #include "components/sync_driver/sync_driver_switches.h"
@@ skipping 33 matching lines @@
 
 #if defined(ENABLE_EXTENSIONS)
 #include "extensions/common/switches.h"
 #endif
 
 #if defined(USE_OZONE)
 #include "ui/ozone/public/ozone_switches.h"
 #endif
 
 using flags_ui::FeatureEntry;
+using flags_ui::kOsMac;
+using flags_ui::kOsWin;
+using flags_ui::kOsLinux;
+using flags_ui::kOsCrOS;
+using flags_ui::kOsAndroid;
+using flags_ui::kOsCrOSOwnerOnly;
 
 namespace about_flags {
 
 namespace {
 
-// Enumeration of OSs.
-enum {
-  kOsMac = 1 << 0,
-  kOsWin = 1 << 1,
-  kOsLinux = 1 << 2,
-  kOsCrOS = 1 << 3,
-  kOsAndroid = 1 << 4,
-  kOsCrOSOwnerOnly = 1 << 5
-};
-
 const unsigned kOsAll = kOsMac | kOsWin | kOsLinux | kOsCrOS | kOsAndroid;
 const unsigned kOsDesktop = kOsMac | kOsWin | kOsLinux | kOsCrOS;
 
-// Adds a |StringValue| to |list| for each platform where |bitmask| indicates
-// whether the entry is available on that platform.
-void AddOsStrings(unsigned bitmask, base::ListValue* list) {
-  struct {
-    unsigned bit;
-    const char* const name;
-  } kBitsToOs[] = {
-    {kOsMac, "Mac"},
-    {kOsWin, "Windows"},
-    {kOsLinux, "Linux"},
-    {kOsCrOS, "Chrome OS"},
-    {kOsAndroid, "Android"},
-    {kOsCrOSOwnerOnly, "Chrome OS (owner only)"},
-  };
-  for (size_t i = 0; i < arraysize(kBitsToOs); ++i) {
-    if (bitmask & kBitsToOs[i].bit)
-      list->Append(new base::StringValue(kBitsToOs[i].name));
-  }
-}
-
-// Convert switch constants to proper CommandLine::StringType strings.
-base::CommandLine::StringType GetSwitchString(const std::string& flag) {
-  base::CommandLine cmd_line(base::CommandLine::NO_PROGRAM);
-  cmd_line.AppendSwitch(flag);
-  DCHECK_EQ(2U, cmd_line.argv().size());
-  return cmd_line.argv()[1];
-}
-
-// Scoops flags from a command line.
-std::set<base::CommandLine::StringType> ExtractFlagsFromCommandLine(
-    const base::CommandLine& cmdline) {
-  std::set<base::CommandLine::StringType> flags;
-  // First do the ones between --flag-switches-begin and --flag-switches-end.
-  base::CommandLine::StringVector::const_iterator first =
-      std::find(cmdline.argv().begin(), cmdline.argv().end(),
-                GetSwitchString(switches::kFlagSwitchesBegin));
-  base::CommandLine::StringVector::const_iterator last =
-      std::find(cmdline.argv().begin(), cmdline.argv().end(),
-                GetSwitchString(switches::kFlagSwitchesEnd));
-  if (first != cmdline.argv().end() && last != cmdline.argv().end())
-    flags.insert(first + 1, last);
-#if defined(OS_CHROMEOS)
-  // Then add those between --policy-switches-begin and --policy-switches-end.
-  first = std::find(cmdline.argv().begin(), cmdline.argv().end(),
-                    GetSwitchString(chromeos::switches::kPolicySwitchesBegin));
-  last = std::find(cmdline.argv().begin(), cmdline.argv().end(),
-                   GetSwitchString(chromeos::switches::kPolicySwitchesEnd));
-  if (first != cmdline.argv().end() && last != cmdline.argv().end())
-    flags.insert(first + 1, last);
-#endif
-  return flags;
-}
-
 const FeatureEntry::Choice kTouchEventsChoices[] = {
   { IDS_GENERIC_EXPERIMENT_CHOICE_AUTOMATIC, "", "" },
   { IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED,
     switches::kTouchEvents,
     switches::kTouchEventsEnabled },
   { IDS_GENERIC_EXPERIMENT_CHOICE_DISABLED,
     switches::kTouchEvents,
     switches::kTouchEventsDisabled }
 };
 
@@ skipping 1942 matching lines @@
     {"enable-appcontainer", IDS_FLAGS_ENABLE_APPCONTAINER_NAME,
      IDS_FLAGS_ENABLE_APPCONTAINER_DESCRIPTION, kOsWin,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableAppContainer,
                                switches::kDisableAppContainer)},
 #endif  // defined(OS_WIN)
     // 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.
 };
 
-// Stores and encapsulates the little state that about:flags has.
-class FlagsState {
+class FlagsStateSingleton {
  public:
-  FlagsState()
-      : feature_entries(kFeatureEntries),
-        num_feature_entries(arraysize(kFeatureEntries)),
-        needs_restart_(false) {}
-  void ConvertFlagsToSwitches(flags_ui::FlagsStorage* flags_storage,
-                              base::CommandLine* command_line,
-                              SentinelsMode sentinels);
-  bool IsRestartNeededToCommitChanges();
-  void SetFeatureEntryEnabled(flags_ui::FlagsStorage* flags_storage,
-                            const std::string& internal_name,
-                            bool enable);
-  void RemoveFlagsSwitches(
-      std::map<std::string, base::CommandLine::StringType>* switch_list);
-  void ResetAllFlags(flags_ui::FlagsStorage* flags_storage);
-  void Reset();
+  FlagsStateSingleton()
+      : flags_state_(kFeatureEntries, arraysize(kFeatureEntries)) {}
+  ~FlagsStateSingleton() {}
 
-  // 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(flags_ui::FlagsStorage* flags_storage,
-                             FlagAccess access,
-                             base::ListValue* supported_entries,
-                             base::ListValue* unsupported_entries);
+  static FlagsStateSingleton* GetInstance() {
+    return base::Singleton<FlagsStateSingleton>::get();
+  }
 
-  void SetFeatureEntries(const FeatureEntry* entries, size_t count);
-  const FeatureEntry* GetFeatureEntries(size_t* count);
-
-  // Returns the singleton instance of this class
-  static FlagsState* GetInstance() {
-    return base::Singleton<FlagsState>::get();
+  static flags_ui::FlagsState* GetFlagsState() {
+    return &GetInstance()->flags_state_;
   }
 
  private:
-  // Keeps track of affected switches for each FeatureEntry, based on which
-  // choice is selected for it.
-  struct SwitchEntry {
-    // Corresponding base::Feature to toggle.
-    std::string feature_name;
+  flags_ui::FlagsState flags_state_;
 
-    // If |feature_name| is not empty, the state (enable/disabled) to set.
-    bool feature_state;
-
-    // The name of the switch to add.
-    std::string switch_name;
-
-    // If |switch_name| is not empty, the value of the switch to set.
-    std::string switch_value;
-
-    SwitchEntry() : feature_state(false) {}
-  };
-
-  // Adds mapping to |name_to_switch_map| to set the given switch name/value.
-  void AddSwitchMapping(const std::string& key,
-                        const std::string& switch_name,
-                        const std::string& switch_value,
-                        std::map<std::string, SwitchEntry>* name_to_switch_map);
-
-  // Adds mapping to |name_to_switch_map| to toggle base::Feature |feature_name|
-  // to state |feature_state|.
-  void AddFeatureMapping(
-      const std::string& key,
-      const std::string& feature_name,
-      bool feature_state,
-      std::map<std::string, SwitchEntry>* name_to_switch_map);
-
-  // Updates the switches in |command_line| by applying the modifications
-  // specified in |name_to_switch_map| for each entry in |enabled_entries|.
-  void AddSwitchesToCommandLine(
-      const std::set<std::string>& enabled_entries,
-      const std::map<std::string, SwitchEntry>& name_to_switch_map,
-      SentinelsMode sentinels,
-      base::CommandLine* command_line);
-
-  // Updates |command_line| by merging the value of the --enable-features= or
-  // --disable-features= list (per the |switch_name| param) with corresponding
-  // entries in |feature_switches| that have value |feature_state|. Keeps track
-  // of the changes by updating |appended_switches|.
-  void MergeFeatureCommandLineSwitch(
-      const std::map<std::string, bool>& feature_switches,
-      const char* switch_name,
-      bool feature_state,
-      base::CommandLine* command_line);
-
-  // Removes all entries from prefs::kEnabledLabsExperiments that are unknown,
-  // to prevent this list to become very long as entries are added and removed.
-  void SanitizeList(flags_ui::FlagsStorage* flags_storage);
-
-  void GetSanitizedEnabledFlags(flags_ui::FlagsStorage* flags_storage,
-                                std::set<std::string>* result);
-
-  // Variant of GetSanitizedEnabledFlags that also removes any flags that aren't
-  // enabled on the current platform.
-  void GetSanitizedEnabledFlagsForCurrentPlatform(
-      flags_ui::FlagsStorage* flags_storage,
-      std::set<std::string>* result);
-
-  const FeatureEntry* feature_entries;
-  size_t num_feature_entries;
-
-  bool needs_restart_;
-  std::map<std::string, std::string> flags_switches_;
-
-  // 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);
+  DISALLOW_COPY_AND_ASSIGN(FlagsStateSingleton);
 };
 
-// Adds the internal names for the specified entry to |names|.
-void AddInternalName(const FeatureEntry& e, std::set<std::string>* names) {
-  switch (e.type) {
-    case FeatureEntry::SINGLE_VALUE:
-    case FeatureEntry::SINGLE_DISABLE_VALUE:
-      names->insert(e.internal_name);
-      break;
-    case FeatureEntry::MULTI_VALUE:
-    case FeatureEntry::ENABLE_DISABLE_VALUE:
-    case FeatureEntry::FEATURE_VALUE:
-      for (int i = 0; i < e.num_choices; ++i)
-        names->insert(e.NameForChoice(i));
-      break;
-  }
-}
-
-// Confirms that an entry is valid, used in a DCHECK in
-// SanitizeList below.
-bool ValidateFeatureEntry(const FeatureEntry& e) {
-  switch (e.type) {
-    case FeatureEntry::SINGLE_VALUE:
-    case FeatureEntry::SINGLE_DISABLE_VALUE:
-      DCHECK_EQ(0, e.num_choices);
-      DCHECK(!e.choices);
-      return true;
-    case FeatureEntry::MULTI_VALUE:
-      DCHECK_GT(e.num_choices, 0);
-      DCHECK(e.choices);
-      DCHECK(e.choices[0].command_line_switch);
-      DCHECK_EQ('\0', e.choices[0].command_line_switch[0]);
-      return true;
-    case FeatureEntry::ENABLE_DISABLE_VALUE:
-      DCHECK_EQ(3, e.num_choices);
-      DCHECK(!e.choices);
-      DCHECK(e.command_line_switch);
-      DCHECK(e.command_line_value);
-      DCHECK(e.disable_command_line_switch);
-      DCHECK(e.disable_command_line_value);
-      return true;
-    case FeatureEntry::FEATURE_VALUE:
-      DCHECK_EQ(3, e.num_choices);
-      DCHECK(!e.choices);
-      DCHECK(e.feature_name);
-      return true;
-  }
-  NOTREACHED();
-  return false;
-}
-
-void FlagsState::SanitizeList(flags_ui::FlagsStorage* flags_storage) {
-  std::set<std::string> known_entries;
-  for (size_t i = 0; i < num_feature_entries; ++i) {
-    DCHECK(ValidateFeatureEntry(feature_entries[i]));
-    AddInternalName(feature_entries[i], &known_entries);
-  }
-
-  std::set<std::string> enabled_entries = flags_storage->GetFlags();
-
-  std::set<std::string> new_enabled_entries =
-      base::STLSetIntersection<std::set<std::string> >(
-          known_entries, enabled_entries);
-
-  if (new_enabled_entries != enabled_entries)
-    flags_storage->SetFlags(new_enabled_entries);
-}
-
-void FlagsState::GetSanitizedEnabledFlags(flags_ui::FlagsStorage* flags_storage,
-                                          std::set<std::string>* result) {
-  SanitizeList(flags_storage);
-  *result = flags_storage->GetFlags();
-}
-
-bool SkipConditionalFeatureEntry(const FeatureEntry& entry) {
-  version_info::Channel channel = chrome::GetChannel();
-
+bool SkipConditionalFeatureEntry(version_info::Channel channel,
+                                 const FeatureEntry& entry) {
 #if defined(OS_ANDROID)
   // enable-data-reduction-proxy-dev is only available for the Dev/Beta channel.
   if (!strcmp("enable-data-reduction-proxy-dev", entry.internal_name) &&
       channel != version_info::Channel::BETA &&
       channel != version_info::Channel::DEV) {
     return true;
   }
   // enable-data-reduction-proxy-alt is only available for the Dev channel.
   if (!strcmp("enable-data-reduction-proxy-alt", entry.internal_name) &&
       channel != version_info::Channel::DEV) {
@@ skipping 38 matching lines @@
       channel != version_info::Channel::UNKNOWN &&
       channel != version_info::Channel::CANARY &&
       channel != version_info::Channel::DEV) {
     return true;
   }
 #endif
 
   return false;
 }
 
-void FlagsState::GetSanitizedEnabledFlagsForCurrentPlatform(
-    flags_ui::FlagsStorage* flags_storage,
-    std::set<std::string>* result) {
-  GetSanitizedEnabledFlags(flags_storage, result);
-
-  // Filter out any entries that aren't enabled on the current platform.  We
-  // don't remove these from prefs else syncing to a platform with a different
-  // set of entries would be lossy.
-  std::set<std::string> platform_entries;
-  int current_platform = GetCurrentPlatform();
-  for (size_t i = 0; i < num_feature_entries; ++i) {
-    const FeatureEntry& entry = feature_entries[i];
-    if (entry.supported_platforms & current_platform)
-      AddInternalName(entry, &platform_entries);
-#if defined(OS_CHROMEOS)
-    if (feature_entries[i].supported_platforms & kOsCrOSOwnerOnly)
-      AddInternalName(entry, &platform_entries);
-#endif
-  }
-
-  std::set<std::string> new_enabled_entries =
-      base::STLSetIntersection<std::set<std::string> >(
-          platform_entries, *result);
-
-  result->swap(new_enabled_entries);
-}
-
-// Returns true if none of this entry's options have been enabled.
-bool IsDefaultValue(
-    const FeatureEntry& entry,
-    const std::set<std::string>& enabled_entries) {
-  switch (entry.type) {
-    case FeatureEntry::SINGLE_VALUE:
-    case FeatureEntry::SINGLE_DISABLE_VALUE:
-      return enabled_entries.count(entry.internal_name) == 0;
-    case FeatureEntry::MULTI_VALUE:
-    case FeatureEntry::ENABLE_DISABLE_VALUE:
-    case FeatureEntry::FEATURE_VALUE:
-      for (int i = 0; i < entry.num_choices; ++i) {
-        if (enabled_entries.count(entry.NameForChoice(i)) > 0)
-          return false;
-      }
-      return true;
-  }
-  NOTREACHED();
-  return true;
-}
-
-// Returns the Value representing the choice data in the specified entry.
-base::Value* CreateChoiceData(
-    const FeatureEntry& entry,
-    const std::set<std::string>& enabled_entries) {
-  DCHECK(entry.type == FeatureEntry::MULTI_VALUE ||
-         entry.type == FeatureEntry::ENABLE_DISABLE_VALUE ||
-         entry.type == FeatureEntry::FEATURE_VALUE);
-  base::ListValue* result = new base::ListValue;
-  for (int i = 0; i < entry.num_choices; ++i) {
-    base::DictionaryValue* value = new base::DictionaryValue;
-    const std::string name = entry.NameForChoice(i);
-    value->SetString("internal_name", name);
-    value->SetString("description", entry.DescriptionForChoice(i));
-    value->SetBoolean("selected", enabled_entries.count(name) > 0);
-    result->Append(value);
-  }
-  return result;
-}
-
 }  // namespace
 
 void ConvertFlagsToSwitches(flags_ui::FlagsStorage* flags_storage,
                             base::CommandLine* command_line,
-                            SentinelsMode sentinels) {
-  FlagsState::GetInstance()->ConvertFlagsToSwitches(flags_storage,
-                                                    command_line,
-                                                    sentinels);
+                            flags_ui::SentinelsMode sentinels) {
+  if (command_line->HasSwitch(switches::kNoExperiments))
+    return;
+
+  FlagsStateSingleton::GetFlagsState()->ConvertFlagsToSwitches(
+      flags_storage, command_line, sentinels, switches::kEnableFeatures,
+      switches::kDisableFeatures);
 }
 
 bool AreSwitchesIdenticalToCurrentCommandLine(
     const base::CommandLine& new_cmdline,
     const base::CommandLine& active_cmdline,
     std::set<base::CommandLine::StringType>* out_difference) {
-  std::set<base::CommandLine::StringType> new_flags =
-      ExtractFlagsFromCommandLine(new_cmdline);
-  std::set<base::CommandLine::StringType> active_flags =
-      ExtractFlagsFromCommandLine(active_cmdline);
-
-  bool result = false;
-  // Needed because std::equal doesn't check if the 2nd set is empty.
-  if (new_flags.size() == active_flags.size()) {
-    result =
-        std::equal(new_flags.begin(), new_flags.end(), active_flags.begin());
-  }
-
-  if (out_difference && !result) {
-    std::set_symmetric_difference(
-        new_flags.begin(),
-        new_flags.end(),
-        active_flags.begin(),
-        active_flags.end(),
-        std::inserter(*out_difference, out_difference->begin()));
-  }
-
-  return result;
-}
-
-void FlagsState::GetFlagFeatureEntries(flags_ui::FlagsStorage* flags_storage,
-                                       FlagAccess access,
-                                       base::ListValue* supported_entries,
-                                       base::ListValue* unsupported_entries) {
-  std::set<std::string> enabled_entries;
-  GetSanitizedEnabledFlags(flags_storage, &enabled_entries);
-
-  int current_platform = GetCurrentPlatform();
-
-  for (size_t i = 0; i < num_feature_entries; ++i) {
-    const FeatureEntry& entry = feature_entries[i];
-    if (SkipConditionalFeatureEntry(entry))
-      continue;
-
-    base::DictionaryValue* data = new base::DictionaryValue();
-    data->SetString("internal_name", entry.internal_name);
-    data->SetString("name",
-                    l10n_util::GetStringUTF16(entry.visible_name_id));
-    data->SetString("description",
-                    l10n_util::GetStringUTF16(
-                        entry.visible_description_id));
-
-    base::ListValue* supported_platforms = new base::ListValue();
-    AddOsStrings(entry.supported_platforms, supported_platforms);
-    data->Set("supported_platforms", supported_platforms);
-    // True if the switch is not currently passed.
-    bool is_default_value = IsDefaultValue(entry, enabled_entries);
-    data->SetBoolean("is_default", is_default_value);
-
-    switch (entry.type) {
-      case FeatureEntry::SINGLE_VALUE:
-      case FeatureEntry::SINGLE_DISABLE_VALUE:
-        data->SetBoolean(
-            "enabled",
-            (!is_default_value &&
-             entry.type == FeatureEntry::SINGLE_VALUE) ||
-            (is_default_value &&
-             entry.type == FeatureEntry::SINGLE_DISABLE_VALUE));
-        break;
-      case FeatureEntry::MULTI_VALUE:
-      case FeatureEntry::ENABLE_DISABLE_VALUE:
-        data->Set("choices", CreateChoiceData(entry, enabled_entries));
-        break;
-      default:

[Alexei Svitkine (slow), 2015/11/06 21:22:28]

I landed https://codereview.chromium.org/1406023021/ earlier today, can you sync
to that change? Thanks.

[sdefresne, 2015/11/12 11:37:25]

Done.

-        NOTREACHED();
-    }
-
-    bool supported = (entry.supported_platforms & current_platform) != 0;
-#if defined(OS_CHROMEOS)
-    if (access == kOwnerAccessToFlags &&
-        (entry.supported_platforms & kOsCrOSOwnerOnly) != 0) {
-      supported = true;
-    }
+#if !defined(OS_CHROMEOS)
+  const char* extra_flag_sentinel_begin_flag_name = nullptr;
+  const char* extra_flag_sentinel_end_flag_name = nullptr;
+#else
+  const char* extra_flag_sentinel_begin_flag_name =
+      chromeos::switches::kPolicySwitchesBegin;
+  const char* extra_flag_sentinel_end_flag_name =
+      chromeos::switches::kPolicySwitchesEnd;
 #endif
-    if (supported)
-      supported_entries->Append(data);
-    else
-      unsupported_entries->Append(data);
-  }
+  return flags_ui::AreSwitchesIdenticalToCurrentCommandLine(
+      new_cmdline, active_cmdline, out_difference,
+      extra_flag_sentinel_begin_flag_name, extra_flag_sentinel_end_flag_name);
 }
 
 void GetFlagFeatureEntries(flags_ui::FlagsStorage* flags_storage,
-                           FlagAccess access,
+                           flags_ui::FlagAccess access,
                            base::ListValue* supported_entries,
                            base::ListValue* unsupported_entries) {
-  FlagsState::GetInstance()->GetFlagFeatureEntries(flags_storage, access,
-                                                   supported_entries,
-                                                   unsupported_entries);
+  version_info::Channel channel = chrome::GetChannel();
+  FlagsStateSingleton::GetFlagsState()->GetFlagFeatureEntries(
+      flags_storage, access, supported_entries, unsupported_entries,
+      base::Bind(&SkipConditionalFeatureEntry, channel));
 }
 
 bool IsRestartNeededToCommitChanges() {
-  return FlagsState::GetInstance()->IsRestartNeededToCommitChanges();
+  return FlagsStateSingleton::GetFlagsState()->IsRestartNeededToCommitChanges();
 }
 
 void SetFeatureEntryEnabled(flags_ui::FlagsStorage* flags_storage,
                             const std::string& internal_name,
                             bool enable) {
-  FlagsState::GetInstance()->SetFeatureEntryEnabled(flags_storage,
-                                                  internal_name, enable);
+  FlagsStateSingleton::GetFlagsState()->SetFeatureEntryEnabled(
+      flags_storage, internal_name, enable);
 }
 
 void RemoveFlagsSwitches(
     std::map<std::string, base::CommandLine::StringType>* switch_list) {
-  FlagsState::GetInstance()->RemoveFlagsSwitches(switch_list);
+  FlagsStateSingleton::GetFlagsState()->RemoveFlagsSwitches(switch_list);
 }
 
 void ResetAllFlags(flags_ui::FlagsStorage* flags_storage) {
-  FlagsState::GetInstance()->ResetAllFlags(flags_storage);
-}
-
-int GetCurrentPlatform() {
-#if defined(OS_MACOSX)
-  return kOsMac;
-#elif defined(OS_WIN)
-  return kOsWin;
-#elif defined(OS_CHROMEOS)  // Needs to be before the OS_LINUX check.
-  return kOsCrOS;
-#elif defined(OS_LINUX) || defined(OS_OPENBSD)
-  return kOsLinux;
-#elif defined(OS_ANDROID)
-  return kOsAndroid;
-#else
-#error Unknown platform
-#endif
+  FlagsStateSingleton::GetFlagsState()->ResetAllFlags(flags_storage);
 }
 
 void RecordUMAStatistics(flags_ui::FlagsStorage* flags_storage) {
   std::set<std::string> flags = flags_storage->GetFlags();
   for (const std::string& flag : flags) {
     std::string action("AboutFlags_");
     action += flag;
     content::RecordComputedAction(action);
   }
   // Since flag metrics are recorded every startup, add a tick so that the
@@ skipping 28 matching lines @@
     }
     DVLOG(1) << "ReportCustomFlags(): histogram='" << uma_histogram_hame
              << "' '" << flag << "', uma_id=" << uma_id;
 
     // Sparse histogram macro does not cache the histogram, so it's safe
     // to use macro with non-static histogram name here.
     UMA_HISTOGRAM_SPARSE_SLOWLY(uma_histogram_hame, uma_id);
   }
 }
 
-//////////////////////////////////////////////////////////////////////////////
-// FlagsState implementation.
-
-namespace {
-
-void FlagsState::ConvertFlagsToSwitches(flags_ui::FlagsStorage* flags_storage,
-                                        base::CommandLine* command_line,
-                                        SentinelsMode sentinels) {
-  if (command_line->HasSwitch(switches::kNoExperiments))
-    return;
-
-  std::set<std::string> enabled_entries;
-
-  GetSanitizedEnabledFlagsForCurrentPlatform(flags_storage, &enabled_entries);
-
-  std::map<std::string, SwitchEntry> name_to_switch_map;
-  for (size_t i = 0; i < num_feature_entries; ++i) {
-    const FeatureEntry& e = feature_entries[i];
-    switch (e.type) {
-      case FeatureEntry::SINGLE_VALUE:
-      case FeatureEntry::SINGLE_DISABLE_VALUE:
-        AddSwitchMapping(e.internal_name, e.command_line_switch,
-                         e.command_line_value, &name_to_switch_map);
-        break;
-      case FeatureEntry::MULTI_VALUE:
-        for (int j = 0; j < e.num_choices; ++j) {
-          AddSwitchMapping(e.NameForChoice(j), e.choices[j].command_line_switch,
-                           e.choices[j].command_line_value,
-                           &name_to_switch_map);
-        }
-        break;
-      case FeatureEntry::ENABLE_DISABLE_VALUE:
-        AddSwitchMapping(e.NameForChoice(0), std::string(), std::string(),
-                         &name_to_switch_map);
-        AddSwitchMapping(e.NameForChoice(1), e.command_line_switch,
-                         e.command_line_value, &name_to_switch_map);
-        AddSwitchMapping(e.NameForChoice(2), e.disable_command_line_switch,
-                         e.disable_command_line_value, &name_to_switch_map);
-        break;
-      case FeatureEntry::FEATURE_VALUE:
-        AddFeatureMapping(e.NameForChoice(0), std::string(), false,
-                          &name_to_switch_map);
-        AddFeatureMapping(e.NameForChoice(1), e.feature_name, true,
-                          &name_to_switch_map);
-        AddFeatureMapping(e.NameForChoice(2), e.feature_name, false,
-                          &name_to_switch_map);
-        break;
-    }
-  }
-
-  AddSwitchesToCommandLine(enabled_entries, name_to_switch_map, sentinels,
-                           command_line);
-}
-
-bool FlagsState::IsRestartNeededToCommitChanges() {
-  return needs_restart_;
-}
-
-void FlagsState::SetFeatureEntryEnabled(flags_ui::FlagsStorage* flags_storage,
-                                        const std::string& internal_name,
-                                        bool enable) {
-  size_t at_index = internal_name.find(flags_ui::testing::kMultiSeparator);
-  if (at_index != std::string::npos) {
-    DCHECK(enable);
-    // We're being asked to enable a multi-choice entry. Disable the
-    // currently selected choice.
-    DCHECK_NE(at_index, 0u);
-    const std::string entry_name = internal_name.substr(0, at_index);
-    SetFeatureEntryEnabled(flags_storage, entry_name, false);
-
-    // And enable the new choice, if it is not the default first choice.
-    if (internal_name != entry_name + "@0") {
-      std::set<std::string> enabled_entries;
-      GetSanitizedEnabledFlags(flags_storage, &enabled_entries);
-      needs_restart_ |= enabled_entries.insert(internal_name).second;
-      flags_storage->SetFlags(enabled_entries);
-    }
-    return;
-  }
-
-  std::set<std::string> enabled_entries;
-  GetSanitizedEnabledFlags(flags_storage, &enabled_entries);
-
-  const FeatureEntry* e = nullptr;
-  for (size_t i = 0; i < num_feature_entries; ++i) {
-    if (feature_entries[i].internal_name == internal_name) {
-      e = feature_entries + i;
-      break;
-    }
-  }
-  DCHECK(e);
-
-  if (e->type == FeatureEntry::SINGLE_VALUE) {
-    if (enable)
-      needs_restart_ |= enabled_entries.insert(internal_name).second;
-    else
-      needs_restart_ |= (enabled_entries.erase(internal_name) > 0);
-  } else if (e->type == FeatureEntry::SINGLE_DISABLE_VALUE) {
-    if (!enable)
-      needs_restart_ |= enabled_entries.insert(internal_name).second;
-    else
-      needs_restart_ |= (enabled_entries.erase(internal_name) > 0);
-  } else {
-    if (enable) {
-      // Enable the first choice.
-      needs_restart_ |= enabled_entries.insert(e->NameForChoice(0)).second;
-    } else {
-      // Find the currently enabled choice and disable it.
-      for (int i = 0; i < e->num_choices; ++i) {
-        std::string choice_name = e->NameForChoice(i);
-        if (enabled_entries.find(choice_name) !=
-            enabled_entries.end()) {
-          needs_restart_ = true;
-          enabled_entries.erase(choice_name);
-          // Continue on just in case there's a bug and more than one
-          // entry for this choice was enabled.
-        }
-      }
-    }
-  }
-
-  flags_storage->SetFlags(enabled_entries);
-}
-
-void FlagsState::RemoveFlagsSwitches(
-    std::map<std::string, base::CommandLine::StringType>* switch_list) {
-  for (const auto& entry : flags_switches_)
-    switch_list->erase(entry.first);
-
-  // If feature entries were added to --enable-features= or --disable-features=
-  // lists, remove them here while preserving existing values.
-  for (const auto& entry : appended_switches_) {
-    const auto& switch_name = entry.first;
-    const auto& switch_added_values = entry.second;
-
-    // The below is either a std::string or a base::string16 based on platform.
-    const auto& existing_value = (*switch_list)[switch_name];
-#if defined(OS_WIN)
-    const std::string existing_value_utf8 = base::UTF16ToUTF8(existing_value);
-#else
-    const std::string& existing_value_utf8 = existing_value;
-#endif
-
-    std::vector<std::string> features =
-        base::FeatureList::SplitFeatureListString(existing_value_utf8);
-    std::vector<std::string> remaining_features;
-    // For any featrue name in |features| that is not in |switch_added_values| -
-    // i.e. it wasn't added by about_flags code, add it to |remaining_features|.
-    for (const std::string& feature : features) {
-      if (!ContainsKey(switch_added_values, feature))
-        remaining_features.push_back(feature);
-    }
-
-    // Either remove the flag entirely if |remaining_features| is empty, or set
-    // the new list.
-    if (remaining_features.empty()) {
-      switch_list->erase(switch_name);
-    } else {
-      std::string switch_value = base::JoinString(remaining_features, ",");
-#if defined(OS_WIN)
-      (*switch_list)[switch_name] = base::UTF8ToUTF16(switch_value);
-#else
-      (*switch_list)[switch_name] = switch_value;
-#endif
-    }
-  }
-}
-
-void FlagsState::ResetAllFlags(flags_ui::FlagsStorage* flags_storage) {
-  needs_restart_ = true;
-
-  std::set<std::string> no_entries;
-  flags_storage->SetFlags(no_entries);
-}
-
-void FlagsState::Reset() {
-  needs_restart_ = false;
-  flags_switches_.clear();
-  appended_switches_.clear();
-}
-
-void FlagsState::SetFeatureEntries(const FeatureEntry* entries, size_t count) {
-  feature_entries = entries;
-  num_feature_entries = count;
-}
-
-const FeatureEntry* FlagsState::GetFeatureEntries(size_t* count) {
-  *count = num_feature_entries;
-  return feature_entries;
-}
-
-void FlagsState::AddSwitchMapping(
-    const std::string& key,
-    const std::string& switch_name,
-    const std::string& switch_value,
-    std::map<std::string, SwitchEntry>* name_to_switch_map) {
-  DCHECK(!ContainsKey(*name_to_switch_map, key));
-
-  SwitchEntry* entry = &(*name_to_switch_map)[key];
-  entry->switch_name = switch_name;
-  entry->switch_value = switch_value;
-}
-
-void FlagsState::AddFeatureMapping(
-    const std::string& key,
-    const std::string& feature_name,
-    bool feature_state,
-    std::map<std::string, SwitchEntry>* name_to_switch_map) {
-  DCHECK(!ContainsKey(*name_to_switch_map, key));
-
-  SwitchEntry* entry = &(*name_to_switch_map)[key];
-  entry->feature_name = feature_name;
-  entry->feature_state = feature_state;
-}
-
-void FlagsState::AddSwitchesToCommandLine(
-    const std::set<std::string>& enabled_entries,
-    const std::map<std::string, SwitchEntry>& name_to_switch_map,
-    SentinelsMode sentinels,
-    base::CommandLine* command_line) {
-  std::map<std::string, bool> feature_switches;
-  if (sentinels == kAddSentinels) {
-    command_line->AppendSwitch(switches::kFlagSwitchesBegin);
-    flags_switches_[switches::kFlagSwitchesBegin] = std::string();
-  }
-
-  for (const std::string& entry_name : enabled_entries) {
-    const auto& entry_it = name_to_switch_map.find(entry_name);
-    if (entry_it == name_to_switch_map.end()) {
-      NOTREACHED();
-      continue;
-    }
-
-    const SwitchEntry& entry = entry_it->second;
-    if (!entry.feature_name.empty()) {
-      feature_switches[entry.feature_name] = entry.feature_state;
-    } else if (!entry.switch_name.empty()) {
-      command_line->AppendSwitchASCII(entry.switch_name, entry.switch_value);
-      flags_switches_[entry.switch_name] = entry.switch_value;
-    }
-    // If an entry doesn't match either of the above, then it is likely the
-    // default entry for a FEATURE_VALUE entry. Safe to ignore.
-  }
-
-  if (!feature_switches.empty()) {
-    MergeFeatureCommandLineSwitch(feature_switches, switches::kEnableFeatures,
-                                  true, command_line);
-    MergeFeatureCommandLineSwitch(feature_switches, switches::kDisableFeatures,
-                                  false, command_line);
-  }
-
-  if (sentinels == kAddSentinels) {
-    command_line->AppendSwitch(switches::kFlagSwitchesEnd);
-    flags_switches_[switches::kFlagSwitchesEnd] = std::string();
-  }
-}
-
-void FlagsState::MergeFeatureCommandLineSwitch(
-    const std::map<std::string, bool>& feature_switches,
-    const char* switch_name,
-    bool feature_state,
-    base::CommandLine* command_line) {
-  std::string original_switch_value =
-      command_line->GetSwitchValueASCII(switch_name);
-  std::vector<std::string> features =
-      base::FeatureList::SplitFeatureListString(original_switch_value);
-  // Only add features that don't already exist in the lists.
-  // Note: The ContainsValue() call results in O(n^2) performance, but in
-  // practice n should be very small.
-  for (const auto& entry : feature_switches) {
-    if (entry.second == feature_state &&
-        !ContainsValue(features, entry.first)) {
-      features.push_back(entry.first);
-      appended_switches_[switch_name].insert(entry.first);
-    }
-  }
-  // Update the switch value only if it didn't change. This avoids setting an
-  // empty list or duplicating the same list (since AppendSwitch() adds the
-  // switch to the end but doesn't remove previous ones).
-  std::string switch_value = base::JoinString(features, ",");
-  if (switch_value != original_switch_value)
-    command_line->AppendSwitchASCII(switch_name, switch_value);
-}
-
-}  // namespace
-
 namespace testing {
 
 const base::HistogramBase::Sample kBadSwitchFormatHistogramId = 0;
 
-void ClearState() {
-  FlagsState::GetInstance()->Reset();
-}
-
-void SetFeatureEntries(const FeatureEntry* entries, size_t count) {
-  if (!entries) {
-    entries = kFeatureEntries;
-    count = arraysize(kFeatureEntries);
-  }
-  FlagsState::GetInstance()->SetFeatureEntries(entries, count);
-}
-
 const FeatureEntry* GetFeatureEntries(size_t* count) {
-  return FlagsState::GetInstance()->GetFeatureEntries(count);
+  *count = arraysize(kFeatureEntries);
+  return kFeatureEntries;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags