Fix sky include guards to match Chromium style

sky/engine/core/dom/PositionIterator.h

 /*
  * Copyright (C) 2007, 2008 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
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef PositionIterator_h
-#define PositionIterator_h
+#ifndef SKY_ENGINE_CORE_DOM_POSITIONITERATOR_H_
+#define SKY_ENGINE_CORE_DOM_POSITIONITERATOR_H_
 
 #include "sky/engine/core/dom/Node.h"
 #include "sky/engine/core/dom/NodeTraversal.h"
 #include "sky/engine/core/dom/Position.h"
 
 namespace blink {
 
 // A Position iterator with constant-time
 // increment, decrement, and several predicates on the Position it is at.
 // Conversion to/from Position is O(n) in the offset.
@@ skipping 28 matching lines @@
     bool isCandidate() const;
 
 private:
     RawPtr<Node> m_anchorNode;
     RawPtr<Node> m_nodeAfterPositionInAnchor; // If this is non-null, m_nodeAfterPositionInAnchor->parentNode() == m_anchorNode;
     int m_offsetInAnchor;
 };
 
 } // namespace blink
 
-#endif // PositionIterator_h
+#endif  // SKY_ENGINE_CORE_DOM_POSITIONITERATOR_H_