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

ui/wm/core/focus_controller.h

Index: ui/wm/core/focus_controller.h
diff --git a/ui/wm/core/focus_controller.h b/ui/wm/core/focus_controller.h
index 43d3c608b2138493f070bce4150b24a073edca58..a8ff75f2b7f25c9d8eb4dfe54aaa7fe4a611d3f4 100644
--- a/ui/wm/core/focus_controller.h
+++ b/ui/wm/core/focus_controller.h
@@ -70,7 +70,8 @@ class WM_EXPORT FocusController : public aura::client::ActivationClient,
   void OnGestureEvent(ui::GestureEvent* event) override;
 
   // Overridden from aura::WindowObserver:
-  void OnWindowVisibilityChanged(aura::Window* window, bool visible) override;
+  void OnWindowVisibilityChanged(aura::Window* window, bool visible,
+                                 bool contentVisible) override;
   void OnWindowDestroying(aura::Window* window) override;
   void OnWindowHierarchyChanging(const HierarchyChangeParams& params) override;
   void OnWindowHierarchyChanged(const HierarchyChangeParams& params) override;