Revert of Removed dependency on the UI from the NetworkPortalDetector.

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

Index: chrome/browser/chromeos/login/screens/error_screen.h
diff --git a/chrome/browser/chromeos/login/screens/error_screen.h b/chrome/browser/chromeos/login/screens/error_screen.h
index 66cb7705c8f28f46faafbba8d1d659bb1fee9d3b..bd20d81f9efa0e21734983764cdc0d296949ba0c 100644
--- a/chrome/browser/chromeos/login/screens/error_screen.h
+++ b/chrome/browser/chromeos/login/screens/error_screen.h
@@ -9,6 +9,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "chrome/browser/chromeos/login/login_performer.h"
 #include "chrome/browser/chromeos/login/oobe_display.h"
 #include "chrome/browser/chromeos/login/screens/error_screen_actor_delegate.h"
@@ -24,6 +25,13 @@
                     public ErrorScreenActorDelegate,
                     public LoginPerformer::Delegate {
  public:
+  class Observer {
+   public:
+    virtual ~Observer() {}
+    virtual void OnErrorScreenShow() = 0;
+    virtual void OnErrorScreenHide() = 0;
+  };
+
   enum UIState {
     UI_STATE_UNKNOWN = 0,
     UI_STATE_UPDATE,
@@ -45,6 +53,9 @@
 
   ErrorScreen(ScreenObserver* screen_observer, ErrorScreenActor* actor);
   virtual ~ErrorScreen();
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
 
   // WizardScreen implementation.
   virtual void PrepareToShow() OVERRIDE;
@@ -106,9 +117,11 @@
 
   OobeDisplay::Screen parent_screen_;
 
+  base::WeakPtrFactory<ErrorScreen> weak_factory_;
+
+  ObserverList<Observer> observers_;
+
   scoped_ptr<LoginPerformer> guest_login_performer_;
-
-  base::WeakPtrFactory<ErrorScreen> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ErrorScreen);
 };