Additional checks/calls for cases when WebUI may be already gone but OOBE screen instance is not

chrome/browser/chromeos/login/network_screen_actor.h

 // Copyright (c) 2011 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 CHROME_BROWSER_CHROMEOS_LOGIN_NETWORK_SCREEN_ACTOR_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_NETWORK_SCREEN_ACTOR_H_
 
 #include "base/string16.h"
 
 namespace chromeos {
 
 // Interface for dependency injection between NetworkScreen and its actual
 // representation, either views based or WebUI. Owned by NetworkScreen.
 class NetworkScreenActor {
  public:
   class Delegate {
    public:
     virtual ~Delegate() {}
+    virtual void OnActorDestroyed(NetworkScreenActor* actor) = 0;
     virtual void OnContinuePressed() = 0;
   };
 
   virtual ~NetworkScreenActor() {}
 
   // Sets screen this actor belongs to.
   virtual void SetDelegate(Delegate* screen) = 0;
 
   // Prepare the contents to showing.
   virtual void PrepareToShow() = 0;
@@ skipping 15 matching lines @@
       bool connecting,
       const string16& network_id) = 0;
 
   // Sets whether continue control is enabled.
   virtual void EnableContinue(bool enabled) = 0;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_NETWORK_SCREEN_ACTOR_H_