Remove shouldPersist from WebPlugin.h.

public/web/WebPlugin.h

 /*
  * Copyright (C) 2009, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2014 Opera Software ASA. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 160 matching lines @@
     enum RotationType {
         RotationType90Clockwise,
         RotationType90Counterclockwise
     };
     // Whether the plugin can rotate the view of its content.
     virtual bool canRotateView() { return false; }
     // Rotates the plugin's view of its content.
     virtual void rotateView(RotationType type) { }
 
     virtual bool isPlaceholder() { return true; }
-    virtual bool shouldPersist() const { return false; }
 
 protected:
     ~WebPlugin() { }
 };
 
 } // namespace blink
 
 #endif