Fix user agent override restore pipeline

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 ac7ff6f674f5ffd3baa8103843d1a01bdea9d003..99fc80544e88ad4a28f72b4d578abb3eef325322 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -126,6 +126,9 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
   // It is safe to delete 'this' from here.
   virtual void WebContentsDestroyed(WebContents* web_contents) {}
 
+  // Called when the user agent override for a WebContents has been changed.
+  virtual void UserAgentOverrideSet(const std::string& user_agent) {}
+
   // IPC::Listener implementation.
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;