WIP - Rough draft of style observation in style of apply hooks.

Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003-2011, 2013, 2014 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
@@ skipping 47 matching lines @@
 class Image;
 class IntSize;
 class Locale;
 class MutableStylePropertySet;
 class PropertySetCSSStyleDeclaration;
 class PseudoElement;
 class ScrollState;
 class ScrollToOptions;
 class ShadowRoot;
 class ShadowRootInit;
+class StyleObserver;
 class StylePropertySet;
 
 enum SpellcheckAttributeState {
     SpellcheckAttributeTrue,
     SpellcheckAttributeFalse,
     SpellcheckAttributeDefault
 };
 
 enum ElementFlags {
     TabIndexWasSetExplicitly = 1 << 0,
@@ skipping 818 matching lines @@
     static PassRefPtrWillBeRawPtr<T> create(const QualifiedName&, Document&)
 #define DEFINE_ELEMENT_FACTORY_WITH_TAGNAME(T) \
     PassRefPtrWillBeRawPtr<T> T::create(const QualifiedName& tagName, Document& document) \
     { \
         return adoptRefWillBeNoop(new T(tagName, document)); \
     }
 
 } // namespace
 
 #endif // Element_h