Enabling page visibility api in the chrome browser.

content/browser/tab_contents/tab_contents.h

Index: content/browser/tab_contents/tab_contents.h
diff --git a/content/browser/tab_contents/tab_contents.h b/content/browser/tab_contents/tab_contents.h
index 99c25cfa46a1f339e52def4cca5ed9bc7d1fd9a3..089899ac47be4bf283d786c6c57b5a1245330e94 100644
--- a/content/browser/tab_contents/tab_contents.h
+++ b/content/browser/tab_contents/tab_contents.h
@@ -774,6 +774,7 @@ class TabContents : public PageNavigator,
   virtual void WorkerCrashed();
   virtual void RequestDesktopNotificationPermission(const GURL& source_origin,
                                                     int callback_context);
+  virtual bool IsHidden() const OVERRIDE;
 
   // RenderViewHostManager::Delegate -------------------------------------------
 
@@ -970,6 +971,11 @@ class TabContents : public PageNavigator,
   // (full-page plugins for now only) permissions.
   int content_restrictions_;
 
+  // We need to know if the tab contents is hidden initially, before the
+  // delegate is set. This variable os only used in the call to IsHidden() if
+  // the delegate is NULL.
+  bool is_initially_hidden_;
+
   DISALLOW_COPY_AND_ASSIGN(TabContents);
 };