Fix sky include guards to match Chromium style

sky/engine/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
  * 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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
-#ifndef Element_h
-#define Element_h
+#ifndef SKY_ENGINE_CORE_DOM_ELEMENT_H_
+#define SKY_ENGINE_CORE_DOM_ELEMENT_H_
 
 #include "gen/sky/core/CSSPropertyNames.h"
 #include "gen/sky/core/HTMLNames.h"
 #include "sky/engine/core/css/CSSPrimitiveValue.h"
 #include "sky/engine/core/dom/Attribute.h"
 #include "sky/engine/core/dom/ContainerNode.h"
 #include "sky/engine/core/dom/ElementData.h"
 #include "sky/engine/core/dom/SpaceSplitString.h"
 #include "sky/engine/core/page/FocusType.h"
 #include "sky/engine/platform/heap/Handle.h"
@@ skipping 548 matching lines @@
 #define DECLARE_ELEMENT_FACTORY_WITH_TAGNAME(T) \
     static PassRefPtr<T> create(const QualifiedName&, Document&)
 #define DEFINE_ELEMENT_FACTORY_WITH_TAGNAME(T) \
     PassRefPtr<T> T::create(const QualifiedName& tagName, Document& document) \
     { \
         return adoptRef(new T(tagName, document)); \
     }
 
 } // namespace
 
-#endif // Element_h
+#endif  // SKY_ENGINE_CORE_DOM_ELEMENT_H_