Fix sky include guards to match Chromium style

sky/engine/core/dom/ShadowTreeStyleSheetCollection.h

 /*
  * 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.
  *
  * 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 ShadowTreeStyleSheetCollection_h
-#define ShadowTreeStyleSheetCollection_h
+#ifndef SKY_ENGINE_CORE_DOM_SHADOWTREESTYLESHEETCOLLECTION_H_
+#define SKY_ENGINE_CORE_DOM_SHADOWTREESTYLESHEETCOLLECTION_H_
 
 #include "sky/engine/core/dom/TreeScopeStyleSheetCollection.h"
 
 namespace blink {
 
 class ShadowRoot;
 class StyleSheetCollection;
 class StyleEngine;
 
 class ShadowTreeStyleSheetCollection final : public TreeScopeStyleSheetCollection {
     WTF_MAKE_NONCOPYABLE(ShadowTreeStyleSheetCollection);
     WTF_MAKE_FAST_ALLOCATED;
 public:
     explicit ShadowTreeStyleSheetCollection(ShadowRoot&);
 
     void updateActiveStyleSheets(StyleEngine*, StyleResolverUpdateMode);
 
 private:
     void collectStyleSheets(StyleEngine*, StyleSheetCollection&);
 };
 
 }
 
-#endif
+#endif  // SKY_ENGINE_CORE_DOM_SHADOWTREESTYLESHEETCOLLECTION_H_