SupervisedUserService: Expose second custodian's name/email

BUG=

Review URL: https://codereview.chromium.org/675183002

Cr-Commit-Position: refs/heads/master@{#301124}
diff --git a/chrome/browser/supervised_user/supervised_user_service.h b/chrome/browser/supervised_user/supervised_user_service.h
index 69a3542..53c63f4d 100644
--- a/chrome/browser/supervised_user/supervised_user_service.h
+++ b/chrome/browser/supervised_user/supervised_user_service.h
@@ -125,6 +125,14 @@
   // empty.
   std::string GetCustodianName() const;
 
+  // Returns the email address of the second custodian, or the empty string
+  // if there is no second custodian.
+  std::string GetSecondCustodianEmailAddress() const;
+
+  // Returns the name of the second custodian, or the email address if the name
+  // is empty, or the empty string is there is no second custodian.
+  std::string GetSecondCustodianName() const;
+
   // Initializes this object. This method does nothing if the profile is not
   // supervised.
   void Init();