Fix sky include guards to match Chromium style

sky/engine/wtf/dtoa/utils.h

 // Copyright 2010 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
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 //       notice, this list of conditions and the following disclaimer.
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 //       with the distribution.
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-#ifndef DOUBLE_CONVERSION_UTILS_H_
-#define DOUBLE_CONVERSION_UTILS_H_
+#ifndef SKY_ENGINE_WTF_DTOA_UTILS_H_
+#define SKY_ENGINE_WTF_DTOA_UTILS_H_
 
 #include <string.h>
 #include "sky/engine/wtf/Assertions.h"
 
 #define UNIMPLEMENTED ASSERT_NOT_REACHED
 #define UNREACHABLE ASSERT_NOT_REACHED
 
 // Double operations detection based on target architecture.
 // Linux uses a 80bit wide floating point stack on x86. This induces double
 // rounding, which in turn leads to wrong results.
@@ skipping 235 matching lines @@
 
     template <class Dest, class Source>
     inline Dest BitCast(Source* source) {
         return BitCast<Dest>(reinterpret_cast<uintptr_t>(source));
     }
 
 }  // namespace double_conversion
 
 } // namespace WTF
 
-#endif  // DOUBLE_CONVERSION_UTILS_H_
+#endif  // SKY_ENGINE_WTF_DTOA_UTILS_H_