[Night Light] Accessibility: Make ChromeVox speak button status on toggles

ash/system/night_light/night_light_toggle_button.h

Index: ash/system/night_light/night_light_toggle_button.h
diff --git a/ash/system/night_light/night_light_toggle_button.h b/ash/system/night_light/night_light_toggle_button.h
index 7a93c8c5a9c34f15b123f4c4be4625b2aac883e3..5f9bdcd0511fcc9438dc35656ded757aef462e4e 100644
--- a/ash/system/night_light/night_light_toggle_button.h
+++ b/ash/system/night_light/night_light_toggle_button.h
@@ -16,10 +16,13 @@ class NightLightToggleButton : public SystemMenuButton {
   explicit NightLightToggleButton(views::ButtonListener* listener);
   ~NightLightToggleButton() override = default;
 
+  // Toggles the status of NightLight.
+  void Toggle();
+
+ private:
   // Updates the icon and its style based on the status of NightLight.
   void Update();
 
- private:
   // views::View:
   void GetAccessibleNodeData(ui::AXNodeData* node_data) override;