Fix sky include guards to match Chromium style

sky/engine/wtf/ArrayPiece.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef ArrayPiece_h
-#define ArrayPiece_h
+#ifndef SKY_ENGINE_WTF_ARRAYPIECE_H_
+#define SKY_ENGINE_WTF_ARRAYPIECE_H_
 
 #include "sky/engine/wtf/Forward.h"
 #include "sky/engine/wtf/WTFExport.h"
 
 namespace WTF {
 
 // This class is for passing around un-owned bytes as a pointer + length.
 // It supports implicit conversion from several other data types.
 //
 // ArrayPiece has the concept of being "null". This is different from an empty
@@ skipping 25 matching lines @@
 
     void* m_data;
     unsigned m_byteLength;
     bool m_isNull;
 };
 
 } // namespace WTF
 
 using WTF::ArrayPiece;
 
-#endif // ArrayPiece_h
+#endif  // SKY_ENGINE_WTF_ARRAYPIECE_H_