Add flag to enable immersive fullscreen for v2 apps

ui/views/widget/widget_deletion_observer.h

 // Copyright (c) 2013 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 UI_VIEWS_WIDGET_WIDGET_DELETION_OBSERVER_H_
 #define UI_VIEWS_WIDGET_WIDGET_DELETION_OBSERVER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "ui/views/views_export.h"
 #include "ui/views/widget/widget_observer.h"
 
 namespace views {
 class Widget;
 
 // A simple WidgetObserver that can be probed for the life of a widget.
-class WidgetDeletionObserver : public WidgetObserver {
+class VIEWS_EXPORT WidgetDeletionObserver : public WidgetObserver {
  public:
   explicit WidgetDeletionObserver(Widget* widget);
   virtual ~WidgetDeletionObserver();
 
   // Returns true if the widget passed in the constructor is still alive.
   bool IsWidgetAlive() { return widget_ != NULL; }
 
   // Overridden from WidgetObserver.
   virtual void OnWidgetDestroying(Widget* widget) OVERRIDE;
 
  private:
   void CleanupWidget();
 
   Widget* widget_;
 
   DISALLOW_COPY_AND_ASSIGN(WidgetDeletionObserver);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_WIDGET_DELETION_OBSERVER_H_