Add avatar syncing for supervised users.

chrome/browser/managed_mode/managed_user_constants.h

Index: chrome/browser/managed_mode/managed_user_constants.h
diff --git a/chrome/browser/managed_mode/managed_user_constants.h b/chrome/browser/managed_mode/managed_user_constants.h
index 6ef2bcb5f5581c040391129633c443ae96110aaf..abb22e111f66f73c672b26e064460e189fc6d1b7 100644
--- a/chrome/browser/managed_mode/managed_user_constants.h
+++ b/chrome/browser/managed_mode/managed_user_constants.h
@@ -22,6 +22,12 @@ extern const char kUserPasswordRecord[];
 // (like Sync), even though we're not signed in.
 extern const char kManagedUserPseudoEmail[];
 
+// Keys for managed user shared settings. These can be configured remotely or
+// locally, and are mapped to preferences by the
+// SupervisedUserPrefMappingService.
+extern const char kChromeAvatarIndex[];
+extern const char kChromeOSAvatarIndex[];
+
 }  // namespace managed_users
 
 #endif  // CHROME_BROWSER_MANAGED_MODE_MANAGED_USER_CONSTANTS_H_