Add WebContentObserver::OnWebContentsLostFocus()

content/public/browser/web_contents_observer.h

Index: content/public/browser/web_contents_observer.h
diff --git a/content/public/browser/web_contents_observer.h b/content/public/browser/web_contents_observer.h
index f29957bdcc97cec5e8ed589c7b6a1d63ae3341bd..db63e84bbaab748015899684840c985512585488 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -423,6 +423,9 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
   // Notification that |contents| has gained focus.
   virtual void OnWebContentsFocused() {}
 
+  // Notification that |contents| has lost focus.
+  virtual void OnWebContentsLostFocus() {}
+
   // Notifes that a CompositorFrame was received from the renderer.
   virtual void DidReceiveCompositorFrame() {}