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

content/browser/web_contents/web_contents_view_aura.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_AURA_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_AURA_H_
 
 #include <vector>
 
 #include "base/memory/ref_counted.h"
@@ skipping 168 matching lines @@
   void OnKeyEvent(ui::KeyEvent* event) override;
   void OnMouseEvent(ui::MouseEvent* event) override;
 
   // Overridden from aura::client::DragDropDelegate:
   void OnDragEntered(const ui::DropTargetEvent& event) override;
   int OnDragUpdated(const ui::DropTargetEvent& event) override;
   void OnDragExited() override;
   int OnPerformDrop(const ui::DropTargetEvent& event) override;
 
   // Overridden from aura::WindowObserver:
-  void OnWindowVisibilityChanged(aura::Window* window, bool visible) override;
-
+  void OnWindowVisibilityChanged(aura::Window* window, bool visible,
+                                 bool content_visible) override;
   // Update the web contents visiblity.
-  void UpdateWebContentsVisibility(bool visible);
+  void UpdateWebContentsVisibility(bool visible, bool content_visible);
 
   scoped_ptr<aura::Window> window_;
 
   // The window that shows the screenshot of the history page during an
   // overscroll navigation gesture.
   scoped_ptr<aura::Window> overscroll_window_;
 
   scoped_ptr<WindowObserver> window_observer_;
 
   // The WebContentsImpl whose contents we display.
@@ skipping 34 matching lines @@
   // On Windows we can run into problems if resources get released within the
   // initialization phase while the content (and its dimensions) are not known.
   bool is_or_was_visible_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsViewAura);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_AURA_H_