[Feature Switch][Media Router] Add required field trials to MR switch.

extensions/common/feature_switch.h

Index: extensions/common/feature_switch.h
diff --git a/extensions/common/feature_switch.h b/extensions/common/feature_switch.h
index c170f9c2fb8f91cd74ef99130fc9630d3d1492e0..93e11f145586b8557fbeeea4542363da730122e0 100644
--- a/extensions/common/feature_switch.h
+++ b/extensions/common/feature_switch.h
@@ -6,6 +6,7 @@
 #define EXTENSIONS_COMMON_FEATURE_SWITCH_H_
 
 #include <string>
+#include <vector>
 
 #include "base/macros.h"
 
@@ -27,7 +28,9 @@ namespace extensions {
 // 3. If there is a switch name, and the switch is present in the command line,
 //    the command line value will be used.
 // 4. If there is a finch experiment associated and applicable to the machine,
-//    the finch value will be used.
+//    the finch value will be used. In order for the feature to be enabled by
+//    finch experiment, the machine must be in the "Enabled" group for the
+//    experiment and all dependent experiments.
 // 5. Otherwise, the default value is used.
 class FeatureSwitch {
  public:
@@ -72,13 +75,19 @@ class FeatureSwitch {
   FeatureSwitch(const char* switch_name,
                 const char* field_trial_name,
                 DefaultValue default_value);
+  FeatureSwitch(const char* switch_name,
+                const char* field_trial_name,
+                const std::vector<const char*>& dependent_field_trials,

[Devlin, 2016/02/09 18:45:14]

"dependent" is the wrong word here - it should probably be "required"

[imcheng, 2016/02/09 21:35:39]

Done.

+                DefaultValue default_value);
   FeatureSwitch(const base::CommandLine* command_line,
                 const char* switch_name,
                 DefaultValue default_value);
   FeatureSwitch(const base::CommandLine* command_line,
                 const char* switch_name,
                 const char* field_trial_name,
+                const std::vector<const char*>& dependent_field_trials,
                 DefaultValue default_value);
+  ~FeatureSwitch();
 
   // Consider using ScopedOverride instead.
   void SetOverrideValue(OverrideValue value);
@@ -89,10 +98,12 @@ class FeatureSwitch {
  private:
   std::string GetLegacyEnableFlag() const;
   std::string GetLegacyDisableFlag() const;
+  bool DependentFieldTrialsEnabled() const;
 
   const base::CommandLine* command_line_;
   const char* switch_name_;
   const char* field_trial_name_;
+  std::vector<const char*> dependent_field_trials_;

[Devlin, 2016/02/09 18:45:14]

this should probably just be std::vector<std::string>

[imcheng, 2016/02/09 21:35:39]

Done.

   bool default_value_;
   OverrideValue override_value_;