Add support for Omaha cohorts to the component updater.

components/update_client/persisted_data.h

Index: components/update_client/persisted_data.h
diff --git a/components/update_client/persisted_data.h b/components/update_client/persisted_data.h
index 6b24e571258cf8d739fa0fdc8fd2ae2bc527bb08..5a4c4c62d2c34604b9f3152cfa79e3ab1cd6c63e 100644
--- a/components/update_client/persisted_data.h
+++ b/components/update_client/persisted_data.h
@@ -52,6 +52,20 @@ class PersistedData {
   // This is called only via update_client's RegisterUpdateClientPreferences.
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
+  // These functions return cohort data for the specified |id|. "Cohort"
+  // indicates the membership of the client in any release channels components
+  // have set up in a machine-readable format, while "CohortName" does so in a
+  // human-readable form. "CohortHint" indicates the client's channel selection
+  // preference.
+  std::string GetCohort(const std::string& id) const;
+  std::string GetCohortHint(const std::string& id) const;
+  std::string GetCohortName(const std::string& id) const;
+
+  // These functions set cohort data for the specified |id|.
+  void SetCohort(const std::string& id, const std::string& cohort);
+  void SetCohortHint(const std::string& id, const std::string& cohort_hint);
+  void SetCohortName(const std::string& id, const std::string& cohort_name);
+
  private:
   base::ThreadChecker thread_checker_;
   PrefService* pref_service_;