Fix build error.

components/os_crypt/key_storage_util_linux.cc

Index: components/os_crypt/key_storage_util_linux.cc
diff --git a/components/os_crypt/key_storage_util_linux.cc b/components/os_crypt/key_storage_util_linux.cc
index d73c31118a48de85cfa4e2aeadf6dc5f2db6cdbf..5be4252e58c11fb257763ecf4ef164d95c77fc64 100644
--- a/components/os_crypt/key_storage_util_linux.cc
+++ b/components/os_crypt/key_storage_util_linux.cc
@@ -42,6 +42,9 @@ SelectedLinuxBackend SelectBackend(const std::string& type,
     case base::nix::DESKTOP_ENVIRONMENT_OTHER:
       return SelectedLinuxBackend::BASIC_TEXT;
   }
+
+  NOTREACHED();
+  return SelectedLinuxBackend::BASIC_TEXT;
 }
 
 }  // namespace os_crypt