Refactor about_flags.cc to make defining enabled/disabled/default flags easier.

chrome/browser/about_flags.h

 // 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.
 
 #ifndef CHROME_BROWSER_ABOUT_FLAGS_H_
 #define CHROME_BROWSER_ABOUT_FLAGS_H_
 
 #include <map>
 #include <string>
 
 #include "base/command_line.h"
+#include "base/string16.h"
 
 class PrefService;
 
 namespace base {
 class ListValue;
 }
 
 namespace about_flags {
 
 // Enumeration of OSs.
 // This is exposed only for testing.
 enum { kOsMac = 1 << 0, kOsWin = 1 << 1, kOsLinux = 1 << 2 , kOsCrOS = 1 << 3,
        kOsAndroid = 1 << 4 };
 
 // Experiment is used internally by about_flags to describe an experiment (and
 // for testing).
 // This is exposed only for testing.
 struct Experiment {
   enum Type {
     // An experiment with a single value. This is typically what you want.
     SINGLE_VALUE,
 
     // The experiment has multiple values only one of which is ever enabled.
     // The first of the values should correspond to a deactivated state for this
     // lab (i.e. no command line option). For MULTI_VALUE experiments the
     // command_line of the Experiment is not used. If the experiment is enabled
     // the command line of the selected Choice is enabled.
     MULTI_VALUE,
+
+    // The experiment has three possible values: Default, Enabled and Disabled.
+    // This should be used for experiments 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,
   };
 
   // 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;
@@ skipping 12 matching lines @@
   // String id of the message containing the experiment's description.
   int visible_description_id;
 
   // The platforms the experiment is available on
   // Needs to be more than a compile-time #ifdef because of profile sync.
   unsigned supported_platforms;  // bitmask
 
   // Type of experiment.
   Type type;
 
-  // The commandline switch and value that are added when this lab is active.
+  // 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.
+  // 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 explictly
+  // disable the feature.
+  const char* disable_command_line_switch;
+  const char* disable_command_line_value;
+
   // 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|.
+  string16 DescriptionForChoice(int index) const;
 };
 
 // Reads the Labs |prefs| (called "Labs" for historical reasons) and adds the
 // commandline flags belonging to the active experiments to |command_line|.
 void ConvertFlagsToSwitches(PrefService* prefs, CommandLine* command_line);
 
 // Get a list of all available experiments. The caller owns the result.
 base::ListValue* GetFlagsExperimentsData(PrefService* prefs);
 
 // Returns true if one of the experiment flags has been flipped since startup.
@@ skipping 14 matching lines @@
 // Returns the value for the current platform. This is one of the values defined
 // by the OS enum above.
 // This is exposed only for testing.
 int GetCurrentPlatform();
 
 // Sends UMA stats about experimental flag usage. This should be called once per
 // startup.
 void RecordUMAStatistics(const PrefService* prefs);
 
 namespace testing {
+
 // Clears internal global state, for unit tests.
 void ClearState();
 
 // Sets the list of experiments. Pass in NULL to use the default set. This does
 // NOT take ownership of the supplied Experiments.
 void SetExperiments(const Experiment* e, size_t count);
 
 // Returns the current set of experiments.
 const Experiment* GetExperiments(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[];
 
 }  // namespace testing
 
 }  // namespace about_flags
 
 #endif  // CHROME_BROWSER_ABOUT_FLAGS_H_