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

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
index c6fc3d741df0f5d11ad26d27bbfb428768bbcb81..adae5b4538c7a2e6bdf9989d6e17cbcfcbd67101 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
@@ -1752,8 +1752,21 @@ uint32_t DesktopWindowTreeHostX11::DispatchEvent(
       previous_bounds_in_pixels_ = bounds_in_pixels_;
       bounds_in_pixels_ = bounds_in_pixels;
 
-      if (origin_changed)
+      if (origin_changed) {
         OnHostMoved(bounds_in_pixels_.origin());
+        // Allows to trigger visibilityChange events while swithcing between
+        // workspaces.
+        ::Screen* screen = DefaultScreenOfDisplay(xdisplay_);
+        int screen_width = WidthOfScreen(screen);
+        int screen_height = HeightOfScreen(screen);
+
+        if (translated_x_in_pixels < 0 || translated_x_in_pixels > screen_width
+            || translated_y_in_pixels < 0 ||
+            translated_y_in_pixels > screen_height)
+          content_window_->SetPageVisibility(false);
+        else
+          content_window_->SetPageVisibility(true);
+      }
 
       if (size_changed) {
         delayed_resize_task_.Reset(base::Bind(