Make Page Visibility API work when the browser window is visible or not

ui/views/widget/desktop_aura/desktop_native_widget_aura.h

Index: ui/views/widget/desktop_aura/desktop_native_widget_aura.h
diff --git a/ui/views/widget/desktop_aura/desktop_native_widget_aura.h b/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
index e92aa8404a80f5d75ec41cab3b3d87c343f0d601..52024ad06977f0ed298f2e2193f4d8d317eeca01 100644
--- a/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
+++ b/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
@@ -234,6 +234,8 @@ class VIEWS_EXPORT DesktopNativeWidgetAura
   void OnHostResized(const aura::WindowTreeHost* host) override;
   void OnHostMoved(const aura::WindowTreeHost* host,
                    const gfx::Point& new_origin) override;
+  void OnHostSetWindowVisibility(const aura::WindowTreeHost* host,
+                                 bool visible) override {}
 
  private:
   friend class FocusManagerEventHandler;