ScreenObserver is renamed to BaseScreenDelegate.

chrome/browser/chromeos/login/screens/hid_detection_screen.h

 // Copyright 2014 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_SCREENS_HID_DETECTION_SCREEN_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_HID_DETECTION_SCREEN_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "chrome/browser/chromeos/login/screens/base_screen.h"
 #include "chrome/browser/chromeos/login/screens/hid_detection_screen_actor.h"
 
 namespace chromeos {
 
 // Representation independent class that controls screen showing warning about
 // HID absence to users.
 class HIDDetectionScreen : public BaseScreen,
                            public HIDDetectionScreenActor::Delegate {
  public:
-  HIDDetectionScreen(ScreenObserver* observer, HIDDetectionScreenActor* actor);
+  HIDDetectionScreen(BaseScreenDelegate* base_screen_delegate,
+                     HIDDetectionScreenActor* actor);
   virtual ~HIDDetectionScreen();
 
   // BaseScreen implementation:
   virtual void PrepareToShow() override;
   virtual void Show() override;
   virtual void Hide() override;
   virtual std::string GetName() const override;
 
   // HIDDetectionScreenActor::Delegate implementation:
   virtual void OnExit() override;
   virtual void OnActorDestroyed(HIDDetectionScreenActor* actor) override;
 
  private:
   HIDDetectionScreenActor* actor_;
 
   DISALLOW_COPY_AND_ASSIGN(HIDDetectionScreen);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_HID_DETECTION_SCREEN_H_