Componentize about_flags::FeatureEntry in flags_ui component.

components/flags_ui/feature_entry.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_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_