Use weak members to cache StyleSheetContents.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2010 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.
  *
@@ skipping 15 matching lines @@
 #include "core/dom/StyleElement.h"
 #include "core/html/HTMLElement.h"
 
 namespace blink {
 
 class HTMLStyleElement;
 
 template<typename T> class EventSender;
 using StyleEventSender = EventSender<HTMLStyleElement>;
 
-class HTMLStyleElement final : public HTMLElement, private StyleElement {
+class CORE_EXPORT HTMLStyleElement final : public HTMLElement, private StyleElement {
     DEFINE_WRAPPERTYPEINFO();
     USING_GARBAGE_COLLECTED_MIXIN(HTMLStyleElement);
 public:
     static HTMLStyleElement* create(Document&, bool createdByParser);
     ~HTMLStyleElement() override;
 
     using StyleElement::sheet;
 
     bool disabled() const;
     void setDisabled(bool);
@@ skipping 22 matching lines @@
     const AtomicString& media() const override;
     const AtomicString& type() const override;
 
     bool m_firedLoad;
     bool m_loadedSheet;
 };
 
 } // namespace blink
 
 #endif // HTMLStyleElement_h