update_engine: fix english

Fix the english for accuracy regarding DLC.

BUG=chromium:897882
TEST=None

Change-Id: I72ab9ecb7903bb5fb35597222cd7c8b1f4244cfc
Reviewed-on: https://chromium-review.googlesource.com/1351359
Commit-Ready: Xiaochu Liu <xiaochu@chromium.org>
Tested-by: Xiaochu Liu <xiaochu@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/client_library/client_dbus.h b/client_library/client_dbus.h
index 0fa2cc3..a186d45 100644
--- a/client_library/client_dbus.h
+++ b/client_library/client_dbus.h
@@ -42,7 +42,7 @@
                      bool at_user_request) override;
 
   bool AttemptInstall(const std::string& omaha_url,
-                      const std::vector<std::string>& dlc_ids) override;
+                      const std::vector<std::string>& dlc_module_ids) override;
 
   bool GetStatus(int64_t* out_last_checked_time,
                  double* out_progress,