Fix use-after-free related to RenderFullScreen

Source/core/dom/FullscreenElementStack.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 109 matching lines @@
 inline Document* FullscreenElementStack::document()
 {
     return lifecycleContext();
 }
 
 void FullscreenElementStack::documentWasDetached()
 {
     m_eventQueue.clear();
 
     if (m_fullScreenRenderer)
-        setFullScreenRenderer(0);
+        m_fullScreenRenderer->destroy();
 
 #if ENABLE(OILPAN)
     m_fullScreenElement = nullptr;
     m_fullScreenElementStack.clear();
 #endif
 
 }
 
 #if !ENABLE(OILPAN)
 void FullscreenElementStack::documentWasDisposed()
@@ skipping 327 matching lines @@
         return;
 
     if (renderer && m_savedPlaceholderRenderStyle) {
         renderer->createPlaceholder(m_savedPlaceholderRenderStyle.release(), m_savedPlaceholderFrameRect);
     } else if (renderer && m_fullScreenRenderer && m_fullScreenRenderer->placeholder()) {
         RenderBlock* placeholder = m_fullScreenRenderer->placeholder();
         renderer->createPlaceholder(RenderStyle::clone(placeholder->style()), placeholder->frameRect());
     }
 
     if (m_fullScreenRenderer)
-        m_fullScreenRenderer->destroy();
+        m_fullScreenRenderer->unwrapRenderer();
     ASSERT(!m_fullScreenRenderer);
 
     m_fullScreenRenderer = renderer;
 }
 
 void FullscreenElementStack::fullScreenRendererDestroyed()
 {
     m_fullScreenRenderer = 0;
 }
 
@@ skipping 83 matching lines @@
 
 void FullscreenElementStack::trace(Visitor* visitor)
 {
     visitor->trace(m_fullScreenElement);
     visitor->trace(m_fullScreenElementStack);
     visitor->trace(m_eventQueue);
     DocumentSupplement::trace(visitor);
 }
 
 } // namespace blink