Device owns the RecoveryUI instance.

Test: mmma -j bootable/recovery
Test: Build and boot into recovery, w/ and w/o enabling quiescent mode
      respectively.
Change-Id: I5d9bb945a6c3c9a3b96199fa0c8071a2f91339a0
diff --git a/stub_ui.h b/stub_ui.h
index fddf4e7..67c338e 100644
--- a/stub_ui.h
+++ b/stub_ui.h
@@ -28,7 +28,7 @@
  public:
   StubRecoveryUI() = default;
 
-  std::string GetLocale() override {
+  std::string GetLocale() const override {
     return "";
   }
   void SetBackground(Icon /* icon */) override {}