Componentize about_flags::FeatureEntry in flags_ui component.

Move FeatureEntry structure definition to components/flags_ui so that
it can be shared with iOS and move the helper macros to a secondary
header file for the same reason.

Move IDS_GENERIC_EXPERIMENT_CHOICE_* strings to flags_ui.grdp.

BUG=551954

Review URL: https://codereview.chromium.org/1415953005

Cr-Commit-Position: refs/heads/master@{#359927}

14 files changed, 255 insertions, 183 deletions

diff --git a/build/ios/grit_whitelist.txt b/build/ios/grit_whitelist.txt
index 943929d..af3c962 100644
--- a/build/ios/grit_whitelist.txt
+++ b/build/ios/grit_whitelist.txt
@@ -426,10 +426,6 @@ IDS_FLAGS_WALLET_SERVICE_USE_SANDBOX_NAME
 IDS_FLAGS_WARNING_HEADER
 IDS_FLAGS_WARNING_TEXT
 IDS_FULLSCREEN
-IDS_GENERIC_EXPERIMENT_CHOICE_AUTOMATIC
-IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT
-IDS_GENERIC_EXPERIMENT_CHOICE_DISABLED
-IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED
 IDS_GROUP_BY_DOMAIN_LABEL
 IDS_GUEST_PROFILE_NAME
 IDS_HARMFUL_V3_EXPLANATION_PARAGRAPH
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index afee6e7..757f7a6 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -5755,18 +5755,6 @@ Keep your key file in a safe place. You will need it to create new versions of y
         </message>
       </if>
 
-      <message name="IDS_GENERIC_EXPERIMENT_CHOICE_AUTOMATIC" desc="Generic 'Automatic' experiment choice option name.">
-        Automatic
-      </message>
-      <message name="IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT" desc="Generic 'Default' experiment choice option name. E.G. shown in multi value options in about:flags.">
-        Default
-      </message>
-      <message name="IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED" desc="Generic 'Enabled' experiment choice option name. E.G. shown in multi value options in about:flags.">
-        Enabled
-      </message>
-      <message name="IDS_GENERIC_EXPERIMENT_CHOICE_DISABLED" desc="Generic 'Disabled' experiment choice option name. E.G. shown in multi value options in about:flags.">
-        Disabled
-      </message>
       <message name="IDS_FLAGS_DISABLE_JAVASCRIPT_HARMONY_SHIPPING_NAME" desc="Title for the flag to disable latest (non-experimental) JavaScript fatures">
         Disable latest stable JavaScript features
       </message>
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 2abd33b..64ba5f8 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -31,6 +31,7 @@
 #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/metrics/metrics_hashes.h"
 #include "components/nacl/common/nacl_switches.h"
@@ -45,6 +46,7 @@
 #include "components/version_info/version_info.h"
 #include "content/public/browser/user_metrics.h"
 #include "content/public/common/content_switches.h"
+#include "grit/components_strings.h"
 #include "media/base/media_switches.h"
 #include "media/midi/midi_switches.h"
 #include "ui/base/l10n/l10n_util.h"
@@ -86,33 +88,9 @@
 #include "ui/ozone/public/ozone_switches.h"
 #endif
 
-namespace about_flags {
+using flags_ui::FeatureEntry;
 
-// Macros to simplify specifying the type. Please refer to the comments on
-// FeatureEntry::Type in the header file, which explain the different entry
-// types and when they should be used.
-#define SINGLE_VALUE_TYPE_AND_VALUE(command_line_switch, switch_value)    \
-  FeatureEntry::SINGLE_VALUE, command_line_switch, switch_value, nullptr, \
-      nullptr, nullptr, nullptr, 0
-#define SINGLE_VALUE_TYPE(command_line_switch) \
-    SINGLE_VALUE_TYPE_AND_VALUE(command_line_switch, "")
-#define SINGLE_DISABLE_VALUE_TYPE_AND_VALUE(command_line_switch, switch_value) \
-  FeatureEntry::SINGLE_DISABLE_VALUE, command_line_switch, switch_value,       \
-      nullptr, nullptr, nullptr, nullptr, 0
-#define SINGLE_DISABLE_VALUE_TYPE(command_line_switch) \
-    SINGLE_DISABLE_VALUE_TYPE_AND_VALUE(command_line_switch, "")
-#define ENABLE_DISABLE_VALUE_TYPE_AND_VALUE(enable_switch, enable_value,   \
-                                            disable_switch, disable_value) \
-  FeatureEntry::ENABLE_DISABLE_VALUE, enable_switch, enable_value,         \
-      disable_switch, disable_value, nullptr, nullptr, 3
-#define ENABLE_DISABLE_VALUE_TYPE(enable_switch, disable_switch) \
-    ENABLE_DISABLE_VALUE_TYPE_AND_VALUE(enable_switch, "", disable_switch, "")
-#define MULTI_VALUE_TYPE(choices)                                         \
-  FeatureEntry::MULTI_VALUE, nullptr, nullptr, nullptr, nullptr, nullptr, \
-      choices, arraysize(choices)
-#define FEATURE_VALUE_TYPE(feature)                                \
-  FeatureEntry::FEATURE_VALUE, nullptr, nullptr, nullptr, nullptr, \
-      &feature, nullptr, 3
+namespace about_flags {
 
 namespace {
 
@@ -2452,35 +2430,6 @@ base::Value* CreateChoiceData(
 
 }  // namespace
 
-std::string FeatureEntry::NameForChoice(int index) const {
-  DCHECK(type == FeatureEntry::MULTI_VALUE ||
-         type == FeatureEntry::ENABLE_DISABLE_VALUE ||
-         type == FeatureEntry::FEATURE_VALUE);
-  DCHECK_LT(index, num_choices);
-  return std::string(internal_name) + testing::kMultiSeparator +
-         base::IntToString(index);
-}
-
-base::string16 FeatureEntry::DescriptionForChoice(int index) const {
-  DCHECK(type == FeatureEntry::MULTI_VALUE ||
-         type == FeatureEntry::ENABLE_DISABLE_VALUE ||
-         type == FeatureEntry::FEATURE_VALUE);
-  DCHECK_LT(index, num_choices);
-  int description_id;
-  if (type == FeatureEntry::ENABLE_DISABLE_VALUE ||
-      type == FeatureEntry::FEATURE_VALUE) {
-    const int kEnableDisableDescriptionIds[] = {
-      IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT,
-      IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED,
-      IDS_GENERIC_EXPERIMENT_CHOICE_DISABLED,
-    };
-    description_id = kEnableDisableDescriptionIds[index];
-  } else {
-    description_id = choices[index].description_id;
-  }
-  return l10n_util::GetStringUTF16(description_id);
-}
-
 void ConvertFlagsToSwitches(flags_ui::FlagsStorage* flags_storage,
                             base::CommandLine* command_line,
                             SentinelsMode sentinels) {
@@ -2729,7 +2678,7 @@ bool FlagsState::IsRestartNeededToCommitChanges() {
 void FlagsState::SetFeatureEntryEnabled(flags_ui::FlagsStorage* flags_storage,
                                         const std::string& internal_name,
                                         bool enable) {
-  size_t at_index = internal_name.find(testing::kMultiSeparator);
+  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
@@ -2956,10 +2905,6 @@ void FlagsState::MergeFeatureCommandLineSwitch(
 
 namespace testing {
 
-// WARNING: '@' is also used in the html file. If you update this constant you
-// also need to update the html file.
-const char kMultiSeparator[] = "@";
-
 const base::HistogramBase::Sample kBadSwitchFormatHistogramId = 0;
 
 void ClearState() {
diff --git a/chrome/browser/about_flags.h b/chrome/browser/about_flags.h
index 70fd642..d16274c 100644
--- a/chrome/browser/about_flags.h
+++ b/chrome/browser/about_flags.h
@@ -14,11 +14,11 @@
 #include "base/command_line.h"
 #include "base/metrics/histogram_base.h"
 #include "base/strings/string16.h"
+#include "components/flags_ui/feature_entry.h"
 
 class PrefService;
 
 namespace base {
-struct Feature;
 class ListValue;
 }
 
@@ -28,102 +28,6 @@ class FlagsStorage;
 
 namespace about_flags {
 
-// FeatureEntry is used by about_flags to describe an experimental feature.
-//
-// Note that features should eventually be either turned on by default with no
-// about_flags entries or deleted. Most feature entries should only be around
-// for a few milestones, until their full launch.
-//
-// This is exposed only for testing.
-struct FeatureEntry {
-  enum Type {
-    // A feature with a single flag value. This is typically what you want.
-    SINGLE_VALUE,
-
-    // A default enabled feature with a single flag value to disable it. Please
-    // consider whether you really need a flag to disable the feature, and even
-    // if so remove the disable flag as soon as it is no longer needed.
-    SINGLE_DISABLE_VALUE,
-
-    // The feature has multiple values only one of which is ever enabled.
-    // The first of the values should correspond to a deactivated state for this
-    // feature (i.e. no command line option). For MULTI_VALUE entries, the
-    // command_line of the FeatureEntry is not used. If the experiment is
-    // enabled the command line of the selected Choice is enabled.
-    MULTI_VALUE,
-
-    // The feature has three possible values: Default, Enabled and Disabled.
-    // This should be used for features that may have their own logic to decide
-    // if the feature should be on when not explicitly specified via about
-    // flags - for example via FieldTrials.
-    ENABLE_DISABLE_VALUE,
-
-    // Corresponds to a base::Feature, per base/feature_list.h. The entry will
-    // have three states: Default, Enabled, Disabled. When not specified or set
-    // to Default, the normal default value of the feature is used.
-    FEATURE_VALUE,
-  };
-
-  // Used for MULTI_VALUE types to describe one of the possible values the user
-  // can select.
-  struct Choice {
-    // ID of the message containing the choice name.
-    int description_id;
-
-    // Command line switch and value to enabled for this choice.
-    const char* command_line_switch;
-    // Simple switches that have no value should use "" for command_line_value.
-    const char* command_line_value;
-  };
-
-  // The internal name of the feature entry. This is never shown to the user.
-  // It _is_ however stored in the prefs file, so you shouldn't change the
-  // name of existing flags.
-  const char* internal_name;
-
-  // String id of the message containing the feature's name.
-  int visible_name_id;
-
-  // String id of the message containing the feature's description.
-  int visible_description_id;
-
-  // The platforms the feature is available on.
-  // Needs to be more than a compile-time #ifdef because of profile sync.
-  unsigned supported_platforms;  // bitmask
-
-  // Type of entry.
-  Type type;
-
-  // The commandline switch and value that are added when this flag is active.
-  // This is different from |internal_name| so that the commandline flag can be
-  // renamed without breaking the prefs file.
-  // This is used if type is SINGLE_VALUE or ENABLE_DISABLE_VALUE.
-  const char* command_line_switch;
-  // Simple switches that have no value should use "" for command_line_value.
-  const char* command_line_value;
-
-  // For ENABLE_DISABLE_VALUE, the command line switch and value to explicitly
-  // disable the feature.
-  const char* disable_command_line_switch;
-  const char* disable_command_line_value;
-
-  // For FEATURE_VALUE, the base::Feature this entry corresponds to.
-  const base::Feature* feature;
-
-  // This is used if type is MULTI_VALUE.
-  const Choice* choices;
-
-  // Number of |choices|.
-  // This is used if type is MULTI_VALUE.
-  int num_choices;
-
-  // Returns the name used in prefs for the choice at the specified |index|.
-  std::string NameForChoice(int index) const;
-
-  // Returns the human readable description for the choice at |index|.
-  base::string16 DescriptionForChoice(int index) const;
-};
-
 // A flag controlling the behavior of the |ConvertFlagsToSwitches| function -
 // whether it should add the sentinel switches around flags.
 enum SentinelsMode { kNoSentinels, kAddSentinels };
@@ -200,14 +104,10 @@ void ClearState();
 
 // Sets the list of feature entries. Pass in null to use the default set. This
 // does NOT take ownership of the supplied |entries|.
-void SetFeatureEntries(const FeatureEntry* entries, size_t count);
+void SetFeatureEntries(const flags_ui::FeatureEntry* entries, size_t count);
 
 // Returns the current set of feature entries.
-const FeatureEntry* GetFeatureEntries(size_t* count);
-
-// Separator used for multi values. Multi values are represented in prefs as
-// name-of-experiment + kMultiSeparator + selected_index.
-extern const char kMultiSeparator[];
+const flags_ui::FeatureEntry* GetFeatureEntries(size_t* count);
 
 // This value is reported as switch histogram ID if switch name has unknown
 // format.
diff --git a/chrome/browser/about_flags_unittest.cc b/chrome/browser/about_flags_unittest.cc
index ca5ebb9..0fbe0d9 100644
--- a/chrome/browser/about_flags_unittest.cc
+++ b/chrome/browser/about_flags_unittest.cc
@@ -26,6 +26,8 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/libxml/chromium/libxml_utils.h"
 
+using flags_ui::FeatureEntry;
+
 namespace about_flags {
 
 namespace {
@@ -528,7 +530,8 @@ TEST_F(AboutFlagsTest, RemoveFlagSwitches_Features) {
     testing::ClearState();
 
     const std::string entry_name = base::StringPrintf(
-        "%s%s%d", kFlags7, testing::kMultiSeparator, cases[i].enabled_choice);
+        "%s%s%d", kFlags7, flags_ui::testing::kMultiSeparator,
+        cases[i].enabled_choice);
     SetFeatureEntryEnabled(&flags_storage_, entry_name, true);
 
     ConvertFlagsToSwitches(&flags_storage_, &command_line, kAddSentinels);
@@ -813,7 +816,8 @@ TEST_F(AboutFlagsTest, NoSeparators) {
   const FeatureEntry* entries = testing::GetFeatureEntries(&count);
   for (size_t i = 0; i < count; ++i) {
     std::string name = entries[i].internal_name;
-    EXPECT_EQ(std::string::npos, name.find(testing::kMultiSeparator)) << i;
+    EXPECT_EQ(std::string::npos, name.find(flags_ui::testing::kMultiSeparator))
+        << i;
   }
 }
 
diff --git a/chrome/browser/profiles/profile_window.cc b/chrome/browser/profiles/profile_window.cc
index 99332cb..b9edb8a 100644
--- a/chrome/browser/profiles/profile_window.cc
+++ b/chrome/browser/profiles/profile_window.cc
@@ -467,12 +467,12 @@ void EnableNewProfileManagementPreview(Profile* profile) {
 #else
   // TODO(rogerta): instead of setting experiment flags and command line
   // args, we should set a profile preference.
-  const about_flags::FeatureEntry entry = {
+  const flags_ui::FeatureEntry entry = {
       kNewProfileManagementExperimentInternalName,
       0,  // string id for title of experiment
       0,  // string id for description of experiment
       0,  // supported platforms
-      about_flags::FeatureEntry::ENABLE_DISABLE_VALUE,
+      flags_ui::FeatureEntry::ENABLE_DISABLE_VALUE,
       switches::kEnableNewProfileManagement,
       "",  // not used with ENABLE_DISABLE_VALUE type
       switches::kDisableNewProfileManagement,
diff --git a/components/flags_ui.gypi b/components/flags_ui.gypi
index a6ab42c..3293221 100644
--- a/components/flags_ui.gypi
+++ b/components/flags_ui.gypi
@@ -11,8 +11,17 @@
       'include_dirs': [
         '..',
       ],
+      'dependencies': [
+        '../base/base.gyp:base',
+        '../base/base.gyp:base_prefs',
+        '../components/components_strings.gyp:components_strings',
+        '../ui/base/ui_base.gyp:ui_base',
+      ],
       'sources': [
         # Note: sources list duplicated in GN build.
+        'flags_ui/feature_entry.cc',
+        'flags_ui/feature_entry.h',
+        'flags_ui/feature_entry_macros.h',
         'flags_ui/flags_ui_constants.cc',
         'flags_ui/flags_ui_constants.h',
         'flags_ui/flags_ui_pref_names.cc',
diff --git a/components/flags_ui/BUILD.gn b/components/flags_ui/BUILD.gn
index 5226765..0678f20 100644
--- a/components/flags_ui/BUILD.gn
+++ b/components/flags_ui/BUILD.gn
@@ -4,6 +4,9 @@
 
 source_set("flags_ui") {
   sources = [
+    "feature_entry.cc",
+    "feature_entry.h",
+    "feature_entry_macros.h",
     "flags_storage.h",
     "flags_ui_constants.cc",
     "flags_ui_constants.h",
@@ -16,5 +19,7 @@ source_set("flags_ui") {
   deps = [
     "//base",
     "//base:prefs",
+    "//components/strings",
+    "//ui/base",
   ]
 }
diff --git a/components/flags_ui/DEPS b/components/flags_ui/DEPS
new file mode 100644
index 0000000..112ca0e
--- /dev/null
+++ b/components/flags_ui/DEPS
@@ -0,0 +1,4 @@
+include_rules = [
+  "+grit/components_strings.h",
+  "+ui/base",
+]
diff --git a/components/flags_ui/OWNERS b/components/flags_ui/OWNERS
index 4298fad..b31ddc1 100644
--- a/components/flags_ui/OWNERS
+++ b/components/flags_ui/OWNERS
@@ -1,3 +1,4 @@
+asvitkine@chromium.org
 bauerb@chromium.org
 dbeam@chromium.org
 estade@chromium.org
diff --git a/components/flags_ui/feature_entry.cc b/components/flags_ui/feature_entry.cc
new file mode 100644
index 0000000..b755697
--- /dev/null
+++ b/components/flags_ui/feature_entry.cc
@@ -0,0 +1,51 @@
+// 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.
+
+#include "components/flags_ui/feature_entry.h"
+
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "grit/components_strings.h"
+#include "ui/base/l10n/l10n_util.h"
+
+namespace flags_ui {
+
+std::string FeatureEntry::NameForChoice(int index) const {
+  DCHECK(type == FeatureEntry::MULTI_VALUE ||
+         type == FeatureEntry::ENABLE_DISABLE_VALUE ||
+         type == FeatureEntry::FEATURE_VALUE);
+  DCHECK_LT(index, num_choices);
+  return std::string(internal_name) + testing::kMultiSeparator +
+         base::IntToString(index);
+}
+
+base::string16 FeatureEntry::DescriptionForChoice(int index) const {
+  DCHECK(type == FeatureEntry::MULTI_VALUE ||
+         type == FeatureEntry::ENABLE_DISABLE_VALUE ||
+         type == FeatureEntry::FEATURE_VALUE);
+  DCHECK_LT(index, num_choices);
+  int description_id;
+  if (type == FeatureEntry::ENABLE_DISABLE_VALUE ||
+      type == FeatureEntry::FEATURE_VALUE) {
+    const int kEnableDisableDescriptionIds[] = {
+        IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT,
+        IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED,
+        IDS_GENERIC_EXPERIMENT_CHOICE_DISABLED,
+    };
+    description_id = kEnableDisableDescriptionIds[index];
+  } else {
+    description_id = choices[index].description_id;
+  }
+  return l10n_util::GetStringUTF16(description_id);
+}
+
+namespace testing {
+
+// WARNING: '@' is also used in the html file. If you update this constant you
+// also need to update the html file.
+const char kMultiSeparator[] = "@";
+
+}  // namespace testing
+
+}  // namespace flags_ui
diff --git a/components/flags_ui/feature_entry.h b/components/flags_ui/feature_entry.h
new file mode 100644
index 0000000..4f7f081
--- /dev/null
+++ b/components/flags_ui/feature_entry.h
@@ -0,0 +1,123 @@
+// 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_FEATURE_ENTRY_H_
+#define COMPONENTS_FLAGS_UI_FEATURE_ENTRY_H_
+
+#include <string>
+
+#include "base/strings/string16.h"
+
+namespace base {
+struct Feature;
+}
+
+namespace flags_ui {
+
+// FeatureEntry is used to describe an experimental feature.
+//
+// Note that features should eventually be either turned on by default with no
+// about_flags entries or deleted. Most feature entries should only be around
+// for a few milestones, until their full launch.
+struct FeatureEntry {
+  enum Type {
+    // A feature with a single flag value. This is typically what you want.
+    SINGLE_VALUE,
+
+    // A default enabled feature with a single flag value to disable it. Please
+    // consider whether you really need a flag to disable the feature, and even
+    // if so remove the disable flag as soon as it is no longer needed.
+    SINGLE_DISABLE_VALUE,
+
+    // The feature has multiple values only one of which is ever enabled.
+    // The first of the values should correspond to a deactivated state for this
+    // feature (i.e. no command line option). For MULTI_VALUE entries, the
+    // command_line of the FeatureEntry is not used. If the experiment is
+    // enabled the command line of the selected Choice is enabled.
+    MULTI_VALUE,
+
+    // The feature has three possible values: Default, Enabled and Disabled.
+    // This should be used for features that may have their own logic to decide
+    // if the feature should be on when not explicitly specified via about
+    // flags - for example via FieldTrials.
+    ENABLE_DISABLE_VALUE,
+
+    // Corresponds to a base::Feature, per base/feature_list.h. The entry will
+    // have three states: Default, Enabled, Disabled. When not specified or set
+    // to Default, the normal default value of the feature is used.
+    FEATURE_VALUE,
+  };
+
+  // Used for MULTI_VALUE types to describe one of the possible values the user
+  // can select.
+  struct Choice {
+    // ID of the message containing the choice name.
+    int description_id;
+
+    // Command line switch and value to enabled for this choice.
+    const char* command_line_switch;
+    // Simple switches that have no value should use "" for command_line_value.
+    const char* command_line_value;
+  };
+
+  // The internal name of the feature entry. This is never shown to the user.
+  // It _is_ however stored in the prefs file, so you shouldn't change the
+  // name of existing flags.
+  const char* internal_name;
+
+  // String id of the message containing the feature's name.
+  int visible_name_id;
+
+  // String id of the message containing the feature's description.
+  int visible_description_id;
+
+  // The platforms the feature is available on.
+  // Needs to be more than a compile-time #ifdef because of profile sync.
+  unsigned supported_platforms;  // bitmask
+
+  // Type of entry.
+  Type type;
+
+  // The commandline switch and value that are added when this flag is active.
+  // This is different from |internal_name| so that the commandline flag can be
+  // renamed without breaking the prefs file.
+  // This is used if type is SINGLE_VALUE or ENABLE_DISABLE_VALUE.
+  const char* command_line_switch;
+
+  // Simple switches that have no value should use "" for command_line_value.
+  const char* command_line_value;
+
+  // For ENABLE_DISABLE_VALUE, the command line switch and value to explicitly
+  // disable the feature.
+  const char* disable_command_line_switch;
+  const char* disable_command_line_value;
+
+  // For FEATURE_VALUE, the base::Feature this entry corresponds to.
+  const base::Feature* feature;
+
+  // This is used if type is MULTI_VALUE.
+  const Choice* choices;
+
+  // Number of |choices|.
+  // This is used if type is MULTI_VALUE.
+  int num_choices;
+
+  // Returns the name used in prefs for the choice at the specified |index|.
+  std::string NameForChoice(int index) const;
+
+  // Returns the human readable description for the choice at |index|.
+  base::string16 DescriptionForChoice(int index) const;
+};
+
+namespace testing {
+
+// Separator used for multi values. Multi values are represented in prefs as
+// name-of-experiment + kMultiSeparator + selected_index.
+extern const char kMultiSeparator[];
+
+}  // namespace
+
+}  // namespace flag_ui
+
+#endif  // COMPONENTS_FLAGS_UI_FEATURE_ENTRY_H_
diff --git a/components/flags_ui/feature_entry_macros.h b/components/flags_ui/feature_entry_macros.h
new file mode 100644
index 0000000..cb36560
--- /dev/null
+++ b/components/flags_ui/feature_entry_macros.h
@@ -0,0 +1,34 @@
+// 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_FEATURE_ENTRY_MACROS_H_
+#define COMPONENTS_FLAGS_UI_FEATURE_ENTRY_MACROS_H_
+
+// Macros to simplify specifying the type of FeatureEntry. Please refer to
+// the comments on FeatureEntry::Type in feature_entry.h, which explain the
+// different entry types and when they should be used.
+#define SINGLE_VALUE_TYPE_AND_VALUE(command_line_switch, switch_value)     \
+  flags_ui::FeatureEntry::SINGLE_VALUE, command_line_switch, switch_value, \
+      nullptr, nullptr, nullptr, nullptr, 0
+#define SINGLE_VALUE_TYPE(command_line_switch) \
+  SINGLE_VALUE_TYPE_AND_VALUE(command_line_switch, "")
+#define SINGLE_DISABLE_VALUE_TYPE_AND_VALUE(command_line_switch, switch_value) \
+  flags_ui::FeatureEntry::SINGLE_DISABLE_VALUE, command_line_switch,           \
+      switch_value, nullptr, nullptr, nullptr, nullptr, 0
+#define SINGLE_DISABLE_VALUE_TYPE(command_line_switch) \
+  SINGLE_DISABLE_VALUE_TYPE_AND_VALUE(command_line_switch, "")
+#define ENABLE_DISABLE_VALUE_TYPE_AND_VALUE(enable_switch, enable_value,     \
+                                            disable_switch, disable_value)   \
+  flags_ui::FeatureEntry::ENABLE_DISABLE_VALUE, enable_switch, enable_value, \
+      disable_switch, disable_value, nullptr, nullptr, 3
+#define ENABLE_DISABLE_VALUE_TYPE(enable_switch, disable_switch) \
+  ENABLE_DISABLE_VALUE_TYPE_AND_VALUE(enable_switch, "", disable_switch, "")
+#define MULTI_VALUE_TYPE(choices)                                          \
+  flags_ui::FeatureEntry::MULTI_VALUE, nullptr, nullptr, nullptr, nullptr, \
+      nullptr, choices, arraysize(choices)
+#define FEATURE_VALUE_TYPE(feature)                                          \
+  flags_ui::FeatureEntry::FEATURE_VALUE, nullptr, nullptr, nullptr, nullptr, \
+      &feature, nullptr, 3
+
+#endif  // COMPONENTS_FLAGS_UI_FEATURE_ENTRY_MACROS_H_
diff --git a/components/flags_ui_strings.grdp b/components/flags_ui_strings.grdp
index 87e70ec..3453b02 100644
--- a/components/flags_ui_strings.grdp
+++ b/components/flags_ui_strings.grdp
@@ -49,4 +49,16 @@
       Flags that apply system-wide can only be set by the owner: <ph name="OWNER_EMAIL">$1<ex>owner@example.com</ex></ph>.
     </message>
   </if>
+  <message name="IDS_GENERIC_EXPERIMENT_CHOICE_AUTOMATIC" desc="Generic 'Automatic' experiment choice option name.">
+    Automatic
+  </message>
+  <message name="IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT" desc="Generic 'Default' experiment choice option name. E.G. shown in multi value options in about:flags.">
+    Default
+  </message>
+  <message name="IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED" desc="Generic 'Enabled' experiment choice option name. E.G. shown in multi value options in about:flags.">
+    Enabled
+  </message>
+  <message name="IDS_GENERIC_EXPERIMENT_CHOICE_DISABLED" desc="Generic 'Disabled' experiment choice option name. E.G. shown in multi value options in about:flags.">
+    Disabled
+  </message>
 </grit-part>