Enabling page visibility api in the chrome browser.

content/renderer/render_view.cc

Index: content/renderer/render_view.cc
diff --git a/content/renderer/render_view.cc b/content/renderer/render_view.cc
index caf265d27c23868a79f3ec3ece6192ea65dbfcba..dac0abae99bbb422ab00969228402b7f33c63b17 100644
--- a/content/renderer/render_view.cc
+++ b/content/renderer/render_view.cc
@@ -3888,6 +3888,7 @@ void RenderView::OnWasHidden() {
   if (webview()) {
     webview()->settings()->setMinimumTimerInterval(
         webkit_glue::kBackgroundTabTimerInterval);
+    webview()->setVisibilityState(WebKit::WebPageVisibilityStateHidden, false);
   }
 
 #if defined(OS_MACOSX)
@@ -3906,6 +3907,7 @@ void RenderView::OnWasRestored(bool needs_repainting) {
   if (webview()) {
     webview()->settings()->setMinimumTimerInterval(
         webkit_glue::kForegroundTabTimerInterval);
+    webview()->setVisibilityState(WebKit::WebPageVisibilityStateVisible, false);
   }
 
 #if defined(OS_MACOSX)
@@ -4106,6 +4108,13 @@ void RenderView::registerProtocolHandler(const WebString& scheme,
                                               title));
 }
 
+WebKit::WebPageVisibilityState RenderView::visibilityState() const {
+  if (is_hidden())
+    return WebKit::WebPageVisibilityStateHidden;
+  else
+    return WebKit::WebPageVisibilityStateVisible;
+}
+
 bool RenderView::IsNonLocalTopLevelNavigation(
     const GURL& url, WebKit::WebFrame* frame, WebKit::WebNavigationType type) {
   // Must be a top level frame.