screen_ui: Drop the parameter in CheckBackgroundTextImages.

ScreenRecoveryUI already has the info in locale_.

Also when showing "Current locale: X/Y" on screen, use 1-based index for
X, so that we have 1 <= X <= Y.

Test: Build anf flash recovery image on aosp_bullhead-userdebug. Choose
      `Run locale test` from UI.
Change-Id: I5dd4de82e63890ddf755f4e23cd2290ad5d50ece
diff --git a/screen_ui.h b/screen_ui.h
index 3e391be..d4923f5 100644
--- a/screen_ui.h
+++ b/screen_ui.h
@@ -148,9 +148,9 @@
 
   void SetColor(UIElement e) const;
 
-  // Check the background text image. Use volume up/down button to cycle through the locales
-  // embedded in the png file, and power button to go back to recovery main menu.
-  void CheckBackgroundTextImages(const std::string& saved_locale);
+  // Checks the background text image, for debugging purpose. It iterates the locales embedded in
+  // the on-device resource files and shows the localized text, for manual inspection.
+  void CheckBackgroundTextImages();
 
  protected:
   // The margin that we don't want to use for showing texts (e.g. round screen, or screen with