Fixing a crash in MediaCustomControlsFullscreenDetector when the page is destroyed

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

 /*
  * Copyright (C) 2007, 2008, 2009, 2010 Apple 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 105 matching lines @@
   // ImageBitmapSource implementation
   IntSize bitmapSourceSize() const override;
   ScriptPromise createImageBitmap(ScriptState*,
                                   EventTarget&,
                                   Optional<IntRect> cropRect,
                                   const ImageBitmapOptions&,
                                   ExceptionState&) override;
 
  private:
   friend class MediaCustomControlsFullscreenDetectorTest;
+  friend class HTMLMediaElementEventListenersTest;
 
   HTMLVideoElement(Document&);
 
   bool layoutObjectIsNeeded(const ComputedStyle&) override;
   LayoutObject* createLayoutObject(const ComputedStyle&) override;
   void attachLayoutTree(const AttachContext& = AttachContext()) override;
   void parseAttribute(const AttributeModificationParams&) override;
   bool isPresentationAttribute(const QualifiedName&) const override;
   void collectStyleForPresentationAttribute(const QualifiedName&,
                                             const AtomicString&,
                                             MutableStylePropertySet*) override;
   bool isURLAttribute(const Attribute&) const override;
   const AtomicString imageSourceURL() const override;
 
   void updateDisplayState() override;
   void didMoveToNewDocument(Document& oldDocument) override;
   void setDisplayMode(DisplayMode) override;
 
   Member<HTMLImageLoader> m_imageLoader;
   Member<MediaCustomControlsFullscreenDetector>
       m_customControlsFullscreenDetector;
 
   AtomicString m_defaultPosterURL;
 };
 
 }  // namespace blink
 
 #endif  // HTMLVideoElement_h