Update class name in PowerButtonMenuBackgroundView.

Bug: None
Change-Id: I1fe55628621fa05d4eaa3dead26bc19d38776be8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1674452Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671853}

ash/system/power/power_button_menu_screen_view.cc

@@ -98,7 +98,7 @@ class PowerButtonMenuScreenView::PowerButtonMenuBackgroundView
 
   // views::View:
   const char* GetClassName() const override {
-    return "PowerButtonMenuScreenView";
+    return "PowerButtonMenuBackgroundView";
   }
 
  private: