Leave ChromeOS system menu open when toggling nightlight.

ash/system/tray/system_menu_button.h

Index: ash/system/tray/system_menu_button.h
diff --git a/ash/system/tray/system_menu_button.h b/ash/system/tray/system_menu_button.h
index c7a381e5e8f96daff1a204ff795d643d9bc6c9ee..d187304804a1811feba4626618e7f45bc1f7204e 100644
--- a/ash/system/tray/system_menu_button.h
+++ b/ash/system/tray/system_menu_button.h
@@ -29,8 +29,8 @@ class SystemMenuButton : public views::ImageButton {
   // to use for the button's accessible and tooltip text.
   SystemMenuButton(views::ButtonListener* listener,
                    TrayPopupInkDropStyle ink_drop_style,
-                   gfx::ImageSkia normal_icon,
-                   gfx::ImageSkia disabled_icon,
+                   const gfx::ImageSkia& normal_icon,
+                   const gfx::ImageSkia& disabled_icon,
                    int accessible_name_id);
 
   // Similar to the above constructor. Just gets a single vector icon and
@@ -42,6 +42,10 @@ class SystemMenuButton : public views::ImageButton {
                    int accessible_name_id);
   ~SystemMenuButton() override;
 
+  // Sets the normal and disabled icons based on that using default menu icon
+  // colors.
+  void SetVectorIcon(const gfx::VectorIcon& icon);
+
   // Explicity sets the ink drop color. Otherwise the default value will be used
   // by TrayPopupUtils::CreateInkDropRipple() and
   // TrayPopupUtils::CreateInkDropHighlight().