Persist plugins over reattach.

Source/platform/Widget.h

 /*
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2008 Collabora Ltd.  All rights reserved.
  * Copyright (C) 2013 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 68 matching lines @@
     bool isSelfVisible() const { return m_selfVisible; } // Whether or not we have been explicitly marked as visible or not.
     bool isParentVisible() const { return m_parentVisible; } // Whether or not our parent is visible.
     bool isVisible() const { return m_selfVisible && m_parentVisible; } // Whether or not we are actually visible.
     virtual void setParentVisible(bool visible) { m_parentVisible = visible; }
     void setSelfVisible(bool v) { m_selfVisible = v; }
 
     virtual bool isFrameView() const { return false; }
     virtual bool isRemoteFrameView() const { return false; }
     virtual bool isPluginView() const { return false; }
     virtual bool isPluginContainer() const { return false; }
-    virtual bool pluginShouldPersist() const { return false; }
     virtual bool isScrollbar() const { return false; }
 
     virtual HostWindow* hostWindow() const { ASSERT_NOT_REACHED(); return 0; }
     virtual void setParent(Widget*);
     Widget* parent() const { return m_parent; }
     Widget* root() const;
 
     virtual void handleEvent(Event*) { }
 
     // It is important for cross-platform code to realize that Mac has flipped coordinates. Therefore any code
@@ skipping 31 matching lines @@
 private:
     RawPtrWillBeMember<Widget> m_parent;
     IntRect m_frame;
     bool m_selfVisible;
     bool m_parentVisible;
 };
 
 } // namespace blink
 
 #endif // Widget_h