Dispose a persisted plugin widget if the content frame is detached.

third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 30 matching lines @@
                                           public FrameOwner {
   USING_GARBAGE_COLLECTED_MIXIN(HTMLFrameOwnerElement);
 
  public:
   ~HTMLFrameOwnerElement() override;
 
   Frame* contentFrame() const { return m_contentFrame; }
   DOMWindow* contentWindow() const;
   Document* contentDocument() const;
 
-  void disconnectContentFrame();
+  virtual void disconnectContentFrame();
 
   // Most subclasses use LayoutPart (either LayoutEmbeddedObject or
   // LayoutIFrame) except for HTMLObjectElement and HTMLEmbedElement which may
   // return any LayoutObject when using fallback content.
   LayoutPart* layoutPart() const;
 
   Document* getSVGDocument(ExceptionState&) const;
 
   virtual bool loadedNonEmptyDocument() const { return false; }
   virtual void didLoadNonEmptyDocument() {}
@@ skipping 95 matching lines @@
 
 DEFINE_TYPE_CASTS(HTMLFrameOwnerElement,
                   FrameOwner,
                   owner,
                   owner->isLocal(),
                   owner.isLocal());
 
 }  // namespace blink
 
 #endif  // HTMLFrameOwnerElement_h